Interphase Twinscope Operation Manual

INTERPHASEINTERPHASE

TWINSCOPE™

OPERATION

MANUAL

1

To Our Customer:

Thank you for choosing the Interphase Twinscope Forward Scanning Sonar. Throughout the
development of this fine product, we have been primarily concerned with creating a unit that offers
the best possible value for your money. Selection of features, ease of use, superior performance
and outstanding reliability were the benchmarks upon which all important design decisions were
made. We feel proud of the Twinscope Forward Scanning Sonar and your satisfaction is very
important to us. To this end, we welcome any comments or suggestions that you might have in
regard to this equipment.

It is very important that you complete and return the WARRANTY REGISTRATION CARD
within 15 days of purchase so that your unit may be protected under the warranty.

Sincerely,

INTERPHASE TECHNOLOGIES, INC.

Interphase Twinscope™ is a trademark of Interphase Technologies, Inc.

©2004 Interphase Technologies, Inc.

Publication # = Twinscope 2.5
Interphase Part # = 25-1038-000

2

Table Of Contents

Important Notice 5
Principle of Operation 6
Display Unit Installation 8
Transducer Installation 12
Basic Operation 20
Getting Started 24
Vertical and Horizontal Scanning Modes 25

Vertical (Probe) Mode:

Set-Up View 28
Demo Program 28
Units of Measure 28
Language Selection 29
Transducer Level Adjustment 29
Forward View (Full Scan) 30
Plot (Track Plot) View 33
Chart View 35
Data View 39
Chart/Plot View 42
Chart/Scan View 44

Horizontal (Sea Scout) Mode:

Set-Up View 47
Alignment Adjustment 48
Forward View (Full Scan) 49
Plot (Track Plot) View 52
Chart View 54
Data View 58
Chart/Plot View 61

Chart/Scan View 63
NMEA 0183 Interface 66
Interpreting the Twinscope’s Forward Vertical (Probe) Display 67

Distance Forward 68

Noise and Sensitivity Adjustments 68

Transducer Sidelobe Effect 68
Interpreting the Twinscope’s Forward Horizontal (Sea Scout) Display 70

Noise and Sensitivity Adjustments 71
Reference Information 73
FAQ’s (Frequently Asked Questions) 76
Maintenance 78
Reset Unit & Calibration 79
Troubleshooting Guide 80
Interference Problems 81
Specifications 82
How To Obtain Service 85
Warranty 87

3

General Information

Thank you for your selection of the Interphase Twinscope

Forward Scanning Sonar. The Twinscope’s ruggedly built,
compact design makes it ideal for installation on nearly any
boat. It will display water depth, bottom conditions and
submerged objects such as fish, or objects in your path, on its
high resolution display. The Twinscope is available with
either two transom a single thru-hull or two thru-hull scanning
sonar depth transducers. In addition, an optional speed/
temperature transducer (either transom or thru-hull) is
available which will enable your Twinscope to display boat
speed, elapsed distance and surface water temperature. Refer
to the accessories part numbers printed in the Transducer
Installation section (Page 19) of this manual, then see your
dealer or call Interphase to order.

The Twinscope has an unprecedented number of advanced
features, in addition to the forward scanning capability, to
make your boating safer and your fishing more productive. Its
high resolution SuperTwist Liquid Crystal Display (LCD)
provides split screen views of 4X magnification zoom and
bottom lock, large digital display and speed and temperature
readings (with the speed/temperature transducer). You will
appreciate the very useful features of fish and depth alarms,
manual or automatic gain control, bottom hardness indicator
and fish symbol identification.

The Twinscope allows operation in your choice of nine
languages: English, French, Italian, Spanish, German, Danish,
Finnish, Swedish, or Greek. Power-off memory saves
language, depth range, gain and contrast settings, screen
advance speed and location in screen menu. Due to its unique
multi-tasking operation, the Twinscope provides instant full
screen updates when switching between modes (no data loss).

If you have your Twinscope interfaced with a Loran-C or GPS
unit, you can take advantage of the included track plot
displays. The Loran-C, DECCA, and GPS track plot displays
on the Twinscope give a whole new dimension, enabling you
to not only see the depths beneath and in front of your boat,
but also to see a graphic display of your boat’s position and
progress over time. The track plot display makes it easy to
find and return to the same fishing spot, or to troll back over
the same productive areas.

To ensure that you receive the maximum benefits available
from the outstanding features of the Interphase Twinscope,

4

please carefully follow the steps outlined in this manual. An
instructive demonstration simulator has been designed into the
Twinscope and we highly recommend that you spend some
time using the demo mode prior to actual use of the unit. We
also recommend that you read this entire manual before
attempting to either install or operate your Twinscope.

WARNING

Navigation based solely on one method or
one instrument should never be practiced.
While the Twinscope can be quite useful in
showing underwater structure and changing
bottom conditions both below and in front of
your vessel, there are many situations and
conditions which can cause erroneous or
distorted readings.

Warranty Information

Interphase provides a 5-Year limited warranty on the
Twinscope Forward Scanning Sonar. We strongly urge you to

read this warranty (reprinted at the back of this manual) and
closely follow its terms and conditions should your Twinscope
require repair. It is highly recommended that you save all
packing materials so that if you should need to send in the unit
for repair, it can be fully protected. If you wrap your display
unit in the original plastic bag and ship it in the box with
cardboard inserts, this will protect your unit from scratches
and shock during shipment.

Should you experience a problem with your Twinscope, first
refer to the Troubleshooting section (Page 80) of this manual.
Most common problems and their solutions are described here.
If problems persist, call Interphase Technical Service at
[phone]. We will be happy to try to assist you, and if
required, we will give you instructions on how to quickly get
your set repaired.

The enclosed warranty registration card must be completed
and returned to Interphase within 15 days of purchase so that
your unit may be protected under the warranty. Failure to
return the warranty card may cause unnecessary delays in
processing your unit for warranty repair.

In addition, there are many situations that can
cause “blind spots” in the Twinscope’s field
of view including the presence of
temperature inversion layers (thermoclines),
water turbulence, and high concentrations of
suspended particles in the water.

While the Twinscope can be considered as a
useful aid to navigation, it should never be
the only means of navigation.

IMPORTANT NOTICE

Since the Twinscope’s Forward Looking
technology is revolutionary, there is a strong
possibility that we will develop many new
and exciting features in the future. We
would like to make sure we can send you
information about these new features and
enhancements.

Please fill out and return the Warranty
Registration Card immediately. This is our
only method to keep in contact with you and
we may want to advise you of future
enhancements to your Twinscope.

If future changes or improvements are made,
software upgrades wil be available for a
nominal charge.

5

Award Winning

Technology

Principle of Operation

The Twinscope Forward Scanning Sonar uses a proprietary
phased array acoustic technology first developed for marine
use by Interphase Technologies. Known as “phased array
ultrasound technology”, its capabilities have been proven in
the medical industry for many years. The amazing video
images provided by medical ultrasound equipment are familiar
to most people and clearly demonstrate the technology’s
ability to show highly defined images in a "real time" or "live
action" mode. Interphase has taken this same technology and
modified it for use in the marine market.

For its pioneering work in developing
Phased Array Scanning Sonar,
Interphase Technologies won the
prestigious IMTEC INNOVATION
AWARD.

The Twinscope Forward Looking
Scanning Sonar is based on this same
award-winning technology.

Present day fish finders/ depth sounders all work on a principle
developed during W.W. II, called SONAR, where acoustic
pulses are used to detect the presence and range or distance to
an underwater object. During the 1950’s, several devices
which used sonar principles were developed and marketed to
fishing and boating enthusiasts to detect the distance to the
bottom (depth) and to indicate the presence of any intervening
submerged objects - such as fish.

An acoustic array is a group of piezoelectric ceramic elements
that are precisely sized and spaced. Each element will send
and receive acoustic pulses, as when used in more
conventional single element depth sounders. However, when
all elements in the array are sending or receiving acoustic
energy at the same time, the entire array behaves like a single
larger element with one important difference: the ability of the
array to concentrate its acoustic energy in different directions,
depending on the different “phasing” of the signals applied or
received by each element. Depending on the signal phasing of
the array, acoustic beams can be directed in an almost
unlimited number of directions. For example, using a 16
element phased array transducer, the Twinscope is capable of
steering the acoustic beam in any of 90 different directions in
either the horizontal or vertical direction. Conventional fixed­beam technology would require the use of 180 different
elements to duplicate this capability. The resulting transducer
would be much too large and costly to be of any practical use.

Since the acoustic beam in the phased array is steered
electronically, requiring no moving parts, it can be quickly and
reliably scanned and re-scanned over a large area. When
displayed, the changing information between subsequent scans
takes on an almost animated quality - for example, showing
movement of underwater targets such as fish or rapidly
changing bottom conditions.

6

In addition to its ability to electronically steer an acoustic
beam, the phased array has other advantages over fixed-beam
technologies, such as: allowing the user to adjust the
transducer beam width, to scan large areas limited only by the
physics of the speed of sound in water (5,000 feet/second), and
the ability to provide nearly real time or live action underwater
views.

When operating, the Twinscope converts a small amount of
electrical current from your battery into ultrasonic sound
pulses, which are then fed to the phased array transducer.
These acoustic pulses travel out from the transducer in a cone
shaped pattern, called the cone angle. When the sound pulse
strikes an underwater object, it is reflected back (echo return),
received by the transducer and converted back into small
electrical impulses. These impulses are amplified, then
displayed as an image on the LCD screen.

The strength of the echo, the depth of the object, and the angle
of the transducer’s beam all affect how the image appears on
the display. Other factors which affect the image include boat
speed relative to the movement, position of the underwater
target and the number of objects reflecting pulses back to the
Twinscope.

The Twinscope’s forward looking display is new and learning
to properly interpret scanning sonar takes both patience and
experience, but once mastered, the Twinscope can offer
tremendous operational advantages over conventional fixed­beam depth sounders. It is also important to realize that while
the Twinscope shows the bottom in both the forward and the
conventional downlooking mode, the presentations are really
quite different. The forward scan shows a view as the beam
“sweeps” across an arc (just like a radar), while the
conventional downlooking view shows a history of repetitive
soundings packed tightly together.

7

Overhead

Shelf/Table

IN-DASH BRACKET INSTALLATION

Optional in-dash bracket available.
Interphase part # 17-0054-008

Installation

Display Unit

The compact size of the Twinscope display unit allows
for easy installation in almost any vessel. To get
maximum performance and life from your unit, the
following guidelines should be considered when
selecting a mounting location:

1) Select a location where the unit is protected from
excessive temperatures. Heat is one of the worst
enemies of electronic components, and will accelerate
component aging, thereby reducing the trouble-free life
of your Twinscope.

2) Mount the display in a location where it will be
convenient to route the power cord and transducer cable.

Power connection

Connect the two-pin plug on the end of the power
supply cable to the power supply jack located at the rear
of the main display unit. Connect the red wire to the
positive terminal and the black wire to the negative
terminal of your boat’s 12 VDC battery.

To minimize electrical interference, carefully route the
power cable so that it does not run parallel or close to
the transducer cable, engine, refrigeration, bilge pump or
any other critical wiring.

IMPORTANT: The Twinscope’s 12 VDC power leads
should go directly to the boat’s battery, distribution
board, or breaker panel. Instability of the display may
result if the unit has to share leads with other electrical
systems aboard your boat.

8

Transducer Connections

It is important that the two leads from the transducer or
transducers be connected to the correct connector on the
rear of the Twinscope . The label on the rear of the
Twinscope shows which transducer cable should be
connected to each of the two 9-pin connectors. If these
cables are reversed, the Twinscope will not scan
correctly.

The Twinscope can be purchased with either transom
mounted or thru-hull transducers.

The standard Twinscope single thru-hull transducer (T1­I200-032) has two cables. Inside the transducer, one
cable connects to the array that does vertical scanning and
the other cable to the array that does the horizontal
scanning. These two cables are identified as either the
Probe (Vertical scanning) or Sea Scout (Horizontal
scanning) by a small label near the connector on each
cable. (see sketch at right)

The Twinscope can also use two seperate thru-hull
transducers - one for the Vertical scanning (Interphase
part number (T1-I200-026) and another for Horizontal
scanning (part number T1-I200-029). These transducers
can be identified by looking at the labels attached near the
connector on each cable.

Rear View of

Twinscope

Display

Vertical
Transducer Ca­ble

12 VDC Power Cable

Horizontal Transducer Cable

For transom mount applications, the Twinscope uses two
seperate transducers, one for Vertical scanning (T1-0200-

025) and the other for Horizontal scanning (T1-0200-

028). These transducers can also be identified by
looking at the labels attached near the connector on each
cable.

The Transducer Installation Section, starting on page 12,
describes the procedures for properly installing the

Twinscope transducer(s) in the vessel.

CHECK LABEL ON TRANSDUCER CABLE

VERTICAL HORIZONTAL

THRU-HULL

TRANSOM
1 THRU HULL

2 THRU-HULLS

T1-0200-025 T1-0200-028
PROBE/

VERTICAL
T1-I200-026 T1-I200-029

SEA SCOUT/
HORIZONTAL

9

Note: The transom mount Probe (Vertical)

and Sea Scout (Horizontal) transducers are

almost identical in appearance. If the labels

are not readable, you can tell the difference by

looking at the mounting brackets. The Sea

Scout has a 1/4” hole drilled as shown in the

sketches below. Also, the Probe’s part number

(on the label) is T1-0200-025, and the Sea

Scout’s number is T1-0200-028.

PROBE

Difference Between Probe and Scout

Transom Transducers

SEA SCOUT

10

Wiring for Power and Transducer
Connectors

The correct pin-out wiring sequences for the power and
transducer connectors are shown at below. DO NOT
SHORTEN THE TRANSDUCER CABLES. If
transducer cables longer than the 30’ length supplied with
your unit is needed, please contact your Interphase
dealer. 30-foot scanning sonar transducer extension
cables are available. (P/N # 04-0014-008)
DANGER: Removal of any connector, disassembly of
transducer, shortening of any cable or use of any cable
other than that supplied by Interphase will void your
warranty. NO EXCEPTIONS.

Cable Connectors (view from front of female

plug)

Power and Transducer

vertical transducer cable

speed/temp & NMEA

horizontal transducer cable

Connections

12 VDC
Battery

Transducers:

1 White 1st element
2 Brown 2nd element
3 Orange 3rd element
4 Yellow 4th element
5 Green 5th element
6 Blue 6th element
7 Violet 7th element
8 Gray 8th element
9 Shield Ground/Return

NMEA & SPEED/TEMP Input

1 Speed Data
2 +5VDC
3 NMEA Data
4 N/C
5 NMEA Return
6 + Temp
7 - Temp
8 Shield/Ground

Power Connector

1 +12 vdc (red)
2 - Ground (black)

SINGLE THRU-HULL
(T1-I200-032)

Transducer Configurations

TWO THRU-HULL'S
(T1-I200-026 - vertical)

(T1-I200-029 - horizontal)

TWO TRANSOM MOUNTS

(T1-0200-025 - vertical)
(T1-0200-028 - horizontal)

11

Scanning Directions.
Vertical scan Probe
mode shown above
and Horizontal Sea
Scout mode below

Transom Mounted Transducer

Forward

Transducer Installation

The Twinscope comes standard with either a single or twin
thru-hull or with two transom mount forward scanning
transducers. An optional speed/temperature transducer is
also available which will allow the Twinscope to display
current boat speed, surface water temperature and elapsed
distance. The following section deals with the installation
of the scanning depth transducers only; installation
instructions for the optional speed/temperature transducer
are included with that accessory

The Twinscope’s uses two 8 element phased arrays (total of
16 elements). In the single thru-hull model all 16 elements
are enclosed in a single transducer. For transom mount
applications (or for the two thru-hull version) two
transducers are required, each containing an 8 element array.
One of the 8 element arrays is positioned to scan vertically
from straight ahead to directly below the boat, while the
other array is positioned to scan forward horizontally from
side to side. The Twinscope has an amazing amount of
capabilities, but it can not perform magic. It can not see
through objects such as your boat’s hull. Therefore, it is
important to position the transducer so that it has as clear a
view as possible of the water directly below and ahead of
your boat, as indicated at left.

The scanning transducer(s) must be positioned properly so
that it scans in the proper direction (i.e. from in front of the
boat to the bottom below). The sketch at left shows the
proper orientation for both the transom mount or the thru­hull transducer(s). NOTE THAT ON THE TRANSOM

MOUNT TRANSDUCERS, THE ROUNDED SIDE
MUST POINT FORWARD, AND ON THE THRU­HULL TRANSDUCER, THE MORE BLUNT AREA
MUST POINT FORWARD.

Thru-Hull Transducer(s)

side view

Forward Direction

top view

General Considerations

DO NOT CUT OR SPLICE YOUR PHASED ARRAY
TRANSDUCER CABLE OR REMOVE THE 9-PIN
CONNECTOR BECAUSE THE SYSTEM
PERFORMANCE MAY BE SERIOUSLY
DEGRADED. THIS ACTION WILL VOID YOUR
WARRANTY. NO EXCEPTIONS.

12

If you need a longer length cable than comes with the
transducer (30’), then purchase the optional 30’
extension cable, Interphase Part # 04-0014-008.

In addition to the above, the following considerations
should be observed:

30’ Extension Cable

1) Choose a location where there is the least amount
of acoustic noise, air bubbles or turbulence caused by
the boat’s movement. The transducer(s) should not be
located nearby or especially directly behind the
propeller.

2) Choose a location where the transducer(s) can be
mounted so that it will be level to the water’s surface
and will not be tilted to either side. Otherwise the
transducer(s) will not scan properly.

3) The transducer(s) must always remain
submerged, regardless of the speed of the boat and
should not be mounted where it could be damaged by
underwater obstacles or when loading on a trailer.

4) DO NOT locate the transducer(s) in the extreme
bow of the boat where it will be subject to intense
turbulence as the boat pounds through the water.

5) DO NOT locate the transducer(s) directly behind
any hull protrusion which will cause the water to be
turbulent when it reaches the transducer(s) or which
will obstruct the transducer’s forward looking view.
For displacement-hull power and sail boats, the thru­hull installation is usually required.

DANGER: DO NOT allow any solvents, i.e. gasoline,
acetone, to come in contact with the transducer(s) or
display unit as this may dissolve the plastic material.

Transom Transducer Installation

The transom transducers are attached to the boat with
heavy-duty stainless kick-up brackets to provide
protection against impact at speeds of 25 - 30 MPH.
When the water force exceeds this setting, the
transducer automatically kicks up and becomes non­operational.

9-pin
Male

Interphase Part #

04-0014-008

9-pin
Female

Transom Mount Bracket in Released

Position

Note: Will not
work at speeds
above 30MPH

Suggested materials required for installation:

♦ Variable speed electric drill with a chuck

capacity of 10mm (3/8”) or larger.

♦ Hole saw or spade bit 19 mm (7/8”) for

transom hole to route cable and
connector

♦ Chamfer bit or 6 mm (1/4”) drill bit
♦ Drill bit No. 28 or 4 mm (9/64”)
♦ Drill bit 3 mm (7/64”)
♦ Marine bedding/sealing compound

♦ Note: Make sure your tooling is sharp and

of the correct diameter before proceeding.

13

Tramsom Mount Locations

Twin Outboards

Cable

Transducer

Cables

18 - 24"

Transom Mounting Location

The main source of vessel acoustic noise is the propeller.
It is very important to position the transducers to
minimize noise pickup and provide as clear a view as
possible of the water ahead of the boat. Study the hull
shape of the vessel carefully to determine the best
transducer mounting location. To achieve optimal
operation the transducers should be mounted in a spot
which:
* Minimizes acoustic noise reception.
* Minimizes the chance that aerated water

will flow across the transducer’s frontal
nose area.

* Optimizes the transducers view of the area

ahead and directly below the boat. (See
diagram below, bottom left)

The transducers can be installed on either side of an
outboard or inboard/outboard engine, or between twin
outboards. For single engine installations, normally 18”
to 24” outboard of the propeller center line is acceptable
and the down stroke side of the propeller is preferred.
Choose a location where water flow is smoothest. For
dual engine installation, just off the center line is usually
acceptable.

Because the transducers rotate back and upwards when
the brackets kick up, they must be mounted in a location
where there is sufficient clearance and headroom to allow
the full kick-up.

Boat’s Hull

Attaching the Transducer and Spray Shield
to the Bracket

Locate the stainless spray shield inside the transducer’s
stainless mounting ears. Make sure spray shield is
orientated as shown in sketch on following page.
Then, assemble the stainless kick-up bracket to the
transducers using the 4 screws, washers and lock nuts
provided. The bracket arms must be mounted outside the
stainless steel mounting ears of the transducer. Do not
fully tighten the lock nuts at this time.

Position the transducer so that it is perpendicular from
side to side and make sure the rounded shaped area is
pointed towards the front of the boat.

Mounting the Transducer to the Boat

After you have selected the optimum mounting location
and have assembled the mounting bracket to the

14

transducer, mount the bracket onto the hull as shown
on the right.

Make sure to position the transducers so they are level
in both the fore and aft and side to side direction so
they will look straight down. Check the location of
your boat’s waterline and position the flat top surface
of the transducer so that it is parallel to the waterline as
shown below.

Note: If the transducers are not mounted so that the
fore and aft direction is parallel to the surface, then the
forward looking display may be distorted where flat
bottoms appear to be slanted upwards or downwards.
After mounting the transducer and actually using the
Twinscope on the water, you may need to readjust the
transducers' mounting for optimum performance.

Mount Transducers So They Will Scan Properly

Rear
View

Waterline

Attach Transducers and Spray Shields to Brackets

Spray Shield

Rear View

Side
view

Transducer
must be
mounted
vertically

Waterline

Flat area on top of
transducer must be
level with waterline

Side
View

Fasten with 4
screws &
nylock
washers as
shown

15

Thru-Hull Transducer Installation

The thru-hull transducer is the recommended choice for larger
boats with in-board engines. Thru-hull mounting is usually
required on larger power and sail craft in order to find a
mounting location free of forward looking hull obstructions.
The Twinscope must have a clear view of the water ahead as it
can not magically see through obstructions such as the vessel’s
hull. Please read the following carefully before starting the
thru-hull installation.

Normally, thru-hull installations are performed by a profes­sional in a boat haul-out facility. We suggest you seek profes­sional assistance before attempting to mount this transducer.

Selecting the Best Location

The best location to mount the thru-hull transducer will vary
with the type of boat. Try to find a location with the smallest
dead rise angle to make installation easiest.

a. On displacement hulls (sailboats, trawlers, etc.) locate the
transducer about 1/3 aft along the waterline. Generally this
provides the best compromise between obtaining aeration-free
water and minimizing propeller noise. The Twinscope’s
transducer can not see through aerated water and water near
the bow and near the keel can be quite aerated. Aeration of the
transducer can be minimized by keeping the transducer
mounted away from the keel and by not mounting too far
forward.

b. On sailboats, the transducer should be mounted where the
acoustic beam will not be shaded by the keel. Try to find an
accessible spot with a minimum dead rise angle.

c. On planing powerboat hulls, the transducer should be
mounted well aft and close to the keel to insure that the
transducer is in contact with the water at higher boat speeds.

On I/O’s, transducer mounting close to the
engine usually yields good results.

(Transducer in front of propeller.)

On inboards always mount the transducer
well ahead of the propeller(s). Turbulence
from props can seriously degrade perform­ance. (Thru-hull installation is recommended.)

d. Mount the transducer on the side of the hull where the
propeller is moving downwards. The upward motion of the
propeller generates pressure waves and pushes bubbles up
against the hull.

16

DO NOT install a bronze transducer housing directly into
an aluminum or steel hull because electrolytic corrosion
will occur.

IMPORTANT:

1) Make sure the water flow across the thru-hull
transducer is bubble and turbulence free at all speeds if
good performance is to be achieved.

2) Make sure the transducer has an unobstructed view of
the water ahead and below the boat.

3) On displacement-hull power boats, the transducer
should be mounted relatively close to the center line of
the hull.

4) Mount the transducer in a place which has reasonable
access from inside the vessel since the transducer’s
bronze nut will require tightening from inside the hull.

Because the Twinscope scans a 12 degree beam from the
surface ahead to directly below the boat, it is important to
make sure that the transducer is installed so that it will
scan in a vertical direction and not off to either side. The
transducer must be mounted so that it’s bronze stem is as
perpendicular to the water line as possible. If necessary,
use a fairing block to properly position the transducer.

Use of a Thru-hull Fairing Block

Nearly all vessels have some dead rise angle at the
transducer mounting location. If the thru-hull transducer
were mounted directly to the hull, the sound beam would
be tilted off the vertical at the same angle as the dead-rise.
Most thru-hull installations will require a fairing block to
insure the transducer is mounted properly.

A fairing block is typically made of teak, mahogany
wood or plastic and should be placed between the
transducer and hull (both inside and outside) to insure
that the transducer’s mounting shaft is perpendicular to
the water’s surface. Make the fairing block as smooth as
possible, and not bigger than the transducer’s face, to
minimize possible turbulence.

Suggested Thru-Hull

Transducer Locations

Fin Keel

Displacement Hull ­Both Power and Sail

After cutting the fairing block, trial fit the block to the
hull. It is very important that the flat top surface of the
transducer be parallel to the water. Because of the
equipment and skill required, we suggest that your
professional boatyard install the fairing block.

Planing Hull

17

MOLDED FAIRING BLOCK

Installing the Thru-hull Transducer

If your installation requires a fairing block, you
may either have one made locally, or purchase
a molded plactic unit from Interphase or your
Interphase distributor.

For this transducer, the molded Fairing Block
Part Number is:

42-2005-000

Mount Transducer so it is Vertical

Waterline

Keep parallel
to waterline !

Hull

Forward

Transducer

1) Drill a 1/8” pilot hole from inside the hull to assure
access to tighten the housing nut and clearance for the
transducer cables. If there is any hull irregularity near the
selected mounting location, it may be desirable to drill from
the outside.

2) Use a 1 - 1/16” hole saw and drill the hole from the
outside of the hull. Sand or clean the area around the hole,
inside and outside to insure that the sealing compound will
adhere properly to the hull. Select a marine grade bedding/
caulking compound and use according to the instructions.

3) Remove the bronze hex nut from the housing and cables.

4) Uncoil the two transducer cables and thread it through
the hole into the inside of the hull.

DANGER: DO NOT apply tension to the transducer
cables as this may sever internal connections. Apply a 1/8”
thick layer of sealant on the upper flat surface of the bronze
housing and fairing block (if used).

5) From the outside of the hull, push the cables and
housing into the 1 - 1/16” hole. Twist the housing slightly
to squeeze out excess sealant. Carefully confirm that the
transducer is aligned so that the blunt rounded end (the
front) is pointed directly toward the front of the boat.

6) Install and tighten bronze hex nut (allow for swelling in
wooden hulls). Do not overtighten nut - especially if a

wooden fairing block is used as it will expand in water.

Waterline

Hull

Keep parallel
to waterline !

7) Remove excess sealant from the outside to assure
smooth water flow over the transducer.

DANGER: Wood hulls and fairing blocks will expand
after the boat is put back into the water, so it is important
that the transducer be only hand-tightened until the wood
fully expands. Otherwise the wood fairing block may
crack.

DANGER: Be sure to check for leaks when the boat is
placed in the water. Allow at least 24 hours after
installation for any leak to appear.

18

DANGER: If the boat is kept in saltwater, it is
recommended that the transducer be coated with an
anti-fouling paint. USE ONLY WATER BASED

ANTI-FOULING PAINT. DO NOT USE KETONE
BASED PAINTS. Ketone based anti-fouling paint

will attack the plastic materials used in the transducer.
See page 78 for recommendations.

OPTIONAL SPEED/TEMPERATURE

TRANSDUCERS

INTERPHASE DESCRIPTION
PART #

T1-0200-021 Transom mount S/T

transducer

T1-0200-027 Thru-hull mount S/T

transducer

04-0009-008 30’ Speed/Temp extension

cable

Both the transom and thru-hull S/T transducers are
separately installed. The transom mount S/T
transducer can be used with the thru-hull depth only
transducer if desired.

To order, call your local Interphase dealer, or
Interphase directly at [phone].

Bronze Nut

Boat’s
Hull

19

Wood or
Plastic
Fairing
Block (Add
sealing
compound
between
faring block
& hull).

Transducer

Interphase Twinscope

Softkeys

Power On/

Off

Short-cut

In this manual you will find
instruction on how to change all
adjustable settings by using the “soft
keys”. However, any setting
adjustment can be done (when the
appropriate menu selection is made)
by turning the control knob.

Settings which can be adjusted by
using the control knob are:

Range
Alarm
Contrast
Sensitivity
Zoom
Sector Width & Direction

LCD screen contrast can be

changed any time while in the
Control Center simply by turning
the control knob.

Basic Operation

The Twinscope has been designed to be as easy to learn and
operate as possible. The raised push-button keys provide a
tactile feel to each operation and the Twinscope responds with
an audible beep each time a key is pressed. All keys necessary
for operation of the unit are on the front panel. The Twinscope
uses a unique approach called “soft keys” along the bottom of
the display. These five keys are labeled by the LCD display and
are controlled by the unit’s software, thus the name “soft keys”.

In addition, a large front panel rotating knob eliminates the need
for multiple button pushes while making gain, depth range,
display contrast and many other adjustments. The knob
provides easy and quick adjustments while giving the user a
familiar style of operation.

The “soft key” buttons allow very easy operation as they almost
guide you along, even though the Twinscope possesses an
amazing number of advanced sonar features. It would take a
considerable number of additional buttons and greatly add to
the unit’s operational complexity if each function had a
dedicated button instead of using the “soft key” approach. In
addition, the use of “soft keys”, coupled with the front panel
adjustment knob, allow for easy future software upgrades which
may include new important features. The use of fixed,
permanently labeled buttons would severely limit any future
upgrade ability.

User Interface

The Twinscope is a very advanced product with many features
never before found on marine instrumentation. In order to
provide these sophisticated new features while continuing to
keep user operation simple and easy to learn, several new design
approaches were adopted. Some of the more significant
approaches are described in the following.

Multi-Tasking Operation

The Twinscope’s Multi-Tasking operation was developed to
make sure your time would not be wasted whenever you change
screen displays. When changing displays with other
conventional systems, the microprocessor has to completely re­assemble a new display picture which can take a considerable
amount of time. These time delays can be very frustrating and
are unnecessary if a Multi-Tasking operating system is used.

20

Pre-Programmed Screen Displays

Rather than ask you to “build” different screen displays
while operating the unit, the Twinscope has seven of the
most valuable LCD screen displays pre-programmed into its
operating system memory. Thanks to the Multi-Tasking
operating system, each of these pre-programmed displays
(known as Views) are always being updated, regardless of
which screen display is presently being used. This means,
for example, that the two Track Plotter’s will continue to
plot and update your vessel’s position - even while you’re
looking at a Zoomed picture of the bottom! Similarly, even
while viewing your vessel’s position on one of the Track
Plot displays, the digital and graphic depth screens are
simultaneously being updated in the background - ready for
immediate access. And, thanks to the lithium battery
memory backup, as described in the next section; ranges,
gain, zoom and other settings are remembered as you go
from View to View and are even remembered when you turn
the unit off.

Internal System Memory

There is nothing so frustrating as having your fishfinder re­start when you start your boat’s engine and having to
completely re-set the range, gain, contrast and all your other
settings. Because the Twinscope contains an internal
lithium memory battery, it remembers all system settings
with the power removed. When you turn your Twinscope
on, it will immediately start in the last View that you used,
complete with the proper range, zoom, gain and other
important settings. Instead of using a non-volatile RAM, a
lithium battery was used to ensure a long error-free memory
life. Most non-volatile RAM’s exhibit increasing errors
with time and can become a serious problem after only
100,000 operations.

Interphase Twinscope

Control
Knob

Cold Cathode Backlight

The Twinscope has the best LCD backlight system
available. It uses a Cold Cathode Fluorescent lamp (CFL)
with exceptionally long life characteristics which greatly
exceed the more common electro-luminescent and
incandescent bulb backlights. In addition to its exceptional
reliability, the cold cathode lamp provides a much more
visible display than other backlight systems. Screen clarity
and contrast are greatly enhanced. The typical half-life
(when output brightness diminishes to 1/2 its original value)
of the cold cathode backlight is in excess of 20,000 hours.
A typical electro-luminescent panel, for comparison, has a
half life of only 2,000 hours!

Pre-Programmed Screen Displays

21

Control Center Softkey Menu

Typical Sub-Menu

Common Soft Key Functions

The Twinscope’s innovative Multi-Tasking operating system
is controlled through the Control Center, where several
different screen displays (views) can easily be selected by the
push of a button. Each of these screens (views) reside in the
Twinscope’s internal memory and all are being updated in the
background, regardless of which screen is currently being
displayed. This allows the Twinscope to provide instant full
screen displays of different features with no data loss on other
screens.

On many of the display screens you will note a recurrence of
the left most soft key labeled “MENU”. When the MENU
soft key is pressed, the Twinscope will return to the Control
Center display. Use of the MENU soft key is required in
order to return to the Control Center where another mode of
operation (i.e. forward looking, track plotting, etc.) can be
chosen.

Power/Backlight Key

Press the "Power/Backlight" key located at the lower right of
the unit to turn the Twinscope on. The unit will respond with
an audible beep when it turns on. Pressing this key again turns
the backlight on and off, each time accompanied by a beep.
To turn the Twinscope off, press this key and hold it down for
several seconds until the unit goes off.

Demo/Simulator Mode

Your Twinscope includes a built-in DEMO simulator
program which makes it easy to practice with the unit and to
get a feeling for its many features before actually using it in
real situations on the water. We highly recommend you run
through this section on operation of the Twinscope with the
DEMO mode activated to first learn basic feature controls.
The DEMO mode can be started from the SETUP menu as
described in the following section.

Split Screen Displays

The Twinscope has several different split screen display
capabilities such as Split Screen Zoom, Split Screen Chart and
Forward Scan, Split Screen Chart and Track Plot, among
others. It is important to realize that whatever is displayed on
the right side of the display is the PRIMARY information.
This means that when you are in split screen displays, the
softkey menus will usually only relate to the right side of the
display.

22

For example, when you are in the split screen Chart/Track
Plotter display, the Track Plot will appear on the right
side of the display and the softkey menu will allow you to
change the Track Plotter settings. In order to make
changes to the downlooking Chart display, you must go
to a display where the Chart display is on the right side of
the display (such as the Chart mode).

In addition to the fact that the softkey menu typically
relates to only the right side of the split screen displays,
other features such as Bottom Hardness and Fish Symbols
will not appear in Zoomed, Bottom Track or Bottom
Locked displays.

Cone Angle & Area Covered to Side

The Twinscope’s Primary Cone Angle is approximately
12 degrees. The Chart at right shows the approximate
width of the cone at different distances from the boat.
Although 50% of the acoustic radiation is concentrated
within this cone, 50% is also outside the cone which
permits the Twinscope to detect targets typically up to
twice the cone angle, (i.e. 24 degrees). This means, for
example, that at 1,000 feet the Twinscope will typically
be able to see targets across a 420 foot width (210 feet
each side of center). See Figure at right. In order to
calculate the approximate width of the primary beam,
divide the forward range by 5. Examples: At 300 feet
forward, the primary cone is approximately 60 feet in
diameter. At 20 feet forward, the primary cone is
approximately 4 feet in diameter

In Split Screen Views, the Softkey Menu

Relates to the Right Side of the Display

1000

210

12 Degree
Cone
Angle

750

158

500

250

105

53

Distance
Forward

or Below

Boat

Width of 12 Degree Acoustic Beam

23

Probe can
typically
see targets
within this
area.

Display Unit

12 VDC

Power
Cable

Display

Mounting

Bracket

Transom Mounted Transducers

Thru-Hull Transducer(s)

Mounting

Knobs

Getting Started

Check to see that all the components shown at left were
included with your Twinscope. If a part is missing, contact
your dealer or the Interphase Customer Service Department

[phone] immediately.
WARNING: DO NOT operate the Twinscope with parts

missing or with parts other than those obtained through
Interphase; doing so could cause a malfunction in the unit. Any
malfunctions to the Twinscope resulting from unauthorized
parts are not covered by warranty.

Turning the Twinscope On

To turn the Twinscope on, press the Power/ Backlight Key
located on the lower right corner of the unit one time. The unit
should sound a beep and the display should be illuminated.

The Control Center

From the Contol Center the Contrast can be adjusted by
turning the Control Knob cockwise to darken, counter
clockwise to lighten. Seven of the most popular displays have
been pre-programmed into the Twinscope’s memory and can be
quickly selected from the Control Center Menu. In the
following sections, these different displays are called “Views”.
They include:

♦ Full Screen Forward View
♦ Full Screen Track Plot View
♦ Full Screen Chart (Conventional) View
♦ Full Screen Set-Up View
♦ Split Screen Data View with Large Digits on left and

Forward looking display on right.

♦ Split Screen View with Chart (Conventional) display on

left and Forward looking display on right.

♦ Split Screen View with Chart (Conventional) display on

left and Track Plot display on right.

Each of these views can be easily selected by pressing the
button below the desired menu selection. Where two selections
are possible, press the button again until you see your desired
view. When first turned on, the Twinscope’s internal memory
automatically sets the starting view to the last one you used
before turning off the power.

The flow chart diagram page 27 shows how to easily navigate
between the Twinscope’s Views. The softkey on the left will
select either the Vertical (Probe) or the Horizontal (Sea Scout)
scanning modes.

24

Vertical (Probe) and Horizontal (Sea
Scout) Scan mode.

Horizontal (Sea Scout) Mode.

It's easy to change the Twinscope's scanning mode
back and forth between horizontal and vertical.
When the Twinscope is in the vertical scanning
mode (scanning the beam from directly ahead to the
bottom below) it offers all of the features of the
popular Interphase Probe sonar. When the
horizontal (Sea Scout) scanning mode is selected,
the Twinscope will act just like our popular Sea
Scout sonar. All of the Twinscope's advanced
features including; full screen downlooking view,
split screen data and track plot views, and
simultaneous split screen forward and downlooking
view, are available in both the vertical or horizontal
forward scan mode.

The horizontal (Sea Scout) mode is often used in
deeper water to hunt for suspended fish, schools of
bait and other submerged targets. The side-to-side
sweeping action of the scanning beam is ideal to
locate forward targets up to 45 degrees on either side
of the bow.

In the horizontal scanning mode, the display will
show the distance and bearing (in degrees) from your
boat's bow. Once targets are located, the vessel can
be steered directly towards the area of interest.

Note suspended

object

approximately 75

feet ahead, 30

degrees to left of

vessel's bow.

Horizontal (Sea Scout) Mode.

Vessel has been

steered toward

suspended target

which now appears

directly ahead.

By switching to the vertical (Probe) scanning mode,
the display can show the depth of suspended targets
and give a view of changing bottom depths and
conditions in front of your boat.

In the vertical scan (Probe) mode, the display can
also show the bottom forward of the boat as shown
at right. Notice that the bottom is slowly falling
away indicating deeper depths ahead.

Vertical (Probe) Mode.

Twinscope switched

to Vertical Scan

(Probe) mode. Note

that suspended

target is at a depth

of approx.15 feet.

25

Switching Between Horizontal and
Vertical Scan Modes

The Twinscope's scanning mode can only be changed
when you are in the Control Center Menu as shown at
left.

Notice that the display above the first softkey on the left
is split into an upper and lower section. The upper
section has a large horizontal arrow and the lower section
has three small up/down arrows.

When the Twinscope is in the horizontal scanning (Sea
Scout) mode, the upper section with the horizontal arrow
will be displayed in reverse video (white arrow on black
background). When in the vertical (Probe) scanning
mode the lower section with the three small up/down
arrows will be shown in reverse video.

To change scanning modes, go to the Control Center
Menu shown at left and press the button below the left
softkey. Each time you press the button the Twinscope
will alternate between scanning modes. The display will
also change to display either the full screen vertical
(Probe) forward scan or the full screen horizontal (Sea
Scout) forward scan view.

Once the desired scanning mode has been selected, you
can press the button beneath the GO softkey (in the
center) to use either full screen view, or anyone of the
other useful views.

When in the vertical (Probe) scan mode, all the other
views on the control panel use the vertical scan. For
example, the split screen data view will show the data on
the left and a vertical forward scan on the right.
Similarly, when the Twinscope is in the horizontal (Sea
Scout) scan mode, all the other views will use the
horizontal scan. In this case, the split screen data view
will show the large digit data on the left of the screen with
a horizontal forward scan view on the right.

A navigational view of all the Twinscope's vertical scan
views are shown at right. The following section describes
each of these views in detail. The section after the next
describes each of the horizontal views in similar detail.

26

VERTICAL SCAN (PROBE) CONTROL CENTER FLOW CHART

PLOT View (Track Plot)

FWD View (Forward Scan)

DATA View (Large Digits)

CHART/PLOT View

CHART View (Conventional)

SET-UP View (Languages, etc.)

27

CHART/SCAN View

Set-Up View

The Twinscope includes a SET-UP View where the
DEMO program can be activated, the units of measure and

language can be selected and the display contrast can be
adjusted. The Twinscope's internal backup battery will
remember all settings for future use.

From the Control Center press the button below the SET-
UP soft key twice to put the display into the SET-UP
View. Then press the button below the “GO” soft key to
use this view. The display should appear as on the left.

Demo Program

We highly recommend you initially operate the Twinscope
in the DEMO mode to familiarize yourself with the many
advanced features of the Twinscope. When using the SET-
UP view, press and hold the soft key below DEMO until
the unit beeps twice and the word “DEMO” on the display
changes to reverse video as shown at left. This will activate
the simulator program. The unit will automatically cycle
through a simulated demonstration of its many features. At
any time, you can press any key to gain control of the
DEMO program to make your own selections and
adjustments. If you do not press any button for about 45
seconds, the unit will automatically resume cycling through
the different demo features on its own.

The pictures shown in the DEMO mode are representations
of what you might see on your Twinscope. In actual use,
the picture you will get can vary significantly depending on
depth, bottom and water conditions, the speed of your boat
and many other factors (see Interpreting The Twinscope’s
Forward Display, beginning on page 67).

To exit the DEMO program either turn the Twinscope off
and back on again, or press the “DEMO” soft key again.

Select Units of Measure

The Twinscope starts with the last units of measure
selected. By pressing the button indicated on the display,
you can use the large front panel knob to choose between
U.S., Nautical and Metric units. Rotate the front panel
knob to select (highlight) the type of display units desired.
Once selected, press any button to save your selection and
exit. The current choice is displayed each time the
“UNITS” soft key is pressed.

28

The choices and their settings are as follows:

Feature U.S. Nautical Metric

Depth/Range Feet Fathoms Meters

(Ft.) (Fa) (M)

Water Temp F F C

(ºF) (ºF) (ºC)

Boat Speed Mi./Hr. Knots Knots

(MPH) (KT) (KT)

Distance Log Miles Naut. Mi Naut.Mi

(Mi) (NMi) (NMi)

Nav. Track Plot Miles Naut. Mi Naut.Mi

(Mi) (NMi) (NMi)

Select Menu Language

The Twinscope allows the selection of 9 operating
languages; English, French, Italian, Spanish, German,
Danish, Finnish, Swedish and Greek may be chosen. To
select the operating language, press the button labeled
LANG. A display window as shown at right will pop up
on the screen showing the available languages and the one
currently selected. Rotate the large front panel knob to
change (highlight) the language selection. Once selected,
press any key to save your selection and exit.

Transducer Level Adjustment

The Twinscope also includes an adjustment to
compensate for transducer installation problems,
especially thru-hull installations, where the transducer is
not perfectly vertical to the water’s surface. This problem
can be caused by improper installation, or by changes in
the boats fore/aft weight.

When the boat is over a known level bottom, the forward
display should show a level line. If the bottom display is
slanted upward or downward (as in the pictures at right),
Press the button labeled “LEVEL” in the SET-UP View
as shown at right above. In the LEVEL menu, notice the
number which indicates the relative amount of correction
in degrees. It is possible to adjust +/- 15 degrees. Positive
numbers will tend to make the bottom slope upwards and
negative numbers will make the bottom slope downwards.
After making the adjustment, go to the forward display
and verify the correction. Once adjusted, the Twinscope’s
memory will retain the setting.

A known level
bottom, but
display slopes
upwards. Correct
by adjusting
LEVEL control in
direction of
negative numbers.

A known level
bottom slopes
downwards on
display. Correct
by adjusting
LEVEL control in
direction of
positive numbers.

29

38.1 MPH

Forward View (Full Screen)

While in the Control Center press the leftmost button until
the display shows the up/down arrows in reverse video as
shown at left. At the top of the screen the current depth
beneath the boat is shown in digital numbers. If the
optional speed/temperature transducer is connected to
theunit, the boat’s speed is displayed just to the left of the
digital depth.

Press the GO button to bring up additional adjustments and
features for this forward looking view. Your display menus
should appear as on the left. Notice that both the
downward depth and forward range are shown by the
digital numbers at the bottom left and the top right side of
the LCD screen. These numbers will change as different
ranges are selected, either automatically or manually.

Range Adjustment

Press the button labeled "RANGE" to bring up the Range
Adjustment soft key menu as shown at left. Press the
button labeled "AUTO" if you would like the Twinscope’s
internal microprocessor to automatically select and adjust
the range as bottom conditions change. To manually adjust
the range, press either the range button labeled "∩" or "∪",
or rotate the large knob. If you make a manual depth
adjustment, the AUTO range mode is turned off and will
remain off until the button labeled AUTO is again selected.
Note: when in the AUTO mode, the soft key labeled
AUTO will be shown in reverse video (white on black). To
return to the main forward looking menu, press the left soft
key labeled "LAST".

Sensitivity Adjustment

Press the soft key labeled "SENS" (for sensitivity) to bring
up the choices available for adjusting the Twinscope's
receiver sensitivity. Press the button labeled "AUTO" so
that the word AUTO is shown in reverse video (white
letters on a black background) if you would like the
Twinscope to automatically adjust its sensitivity for
changing conditions. To manually adjust the sensitivity,
either press the button labeled “- Sens.” or “Sens +” or
rotate the control knob. Note that the soft key shows a
number which indicates the relative sensitivity being used
(+1 to +32). When you choose to manually adjust the
sensitivity, the Twinscope turns off the AUTO sensitivity
mode and it will remain off until the AUTO soft key is
again selected. To exit the sensitivity menu and save your

30

adjustments simply press the soft key labeled “LAST”
to return to the main forward looking menu.

Alarm Adjustment

In the forward looking display or view, alarms may be
set for targets which are shallower than, deeper than, or
within a specific zone of adjustable depth settings.

To adjust or clear the alarm settings, press the soft key
labeled “ALARM” to bring up the forward looking
alarm menu choices. Pressing the "DEEP" or "SHAL."
soft keys brings up sub-menus to set, adjust or clear the
Shallow, Deep and Zone Alarms. As either the up or
down keys are pressed and held down, or the large knob
is rotated, a vertical bar on the left side of the screen
(just below the boat icon) will move to show the area
covered by the depth alarm. In addition, a horizontal
line will appear across the display. Whenever a solidly
displayed target appears at the same depth as that
covered by the alarm bar, the audible alarm sounds to
warn you of underwater targets or changing bottom
conditions. (Note: the horizontal line will disappear a
few seconds after the alarm is adjusted, but the vertical
bar will remain.)

The Shallow Alarm is often used to alert the user to
shallowing bottom conditions and the presence of
underwater targets such as fish, and when activated,
will sound a rapid beeping. The Deep Alarm is often
used in conjunction with the Shallow Alarm to define a
depth range. If the depth becomes less or greater than
the alarm settings, the audio alarm will sound as a
warning. If the Deep alarm is activated, the Twinscope
will make a slow beeping noise. A Zone Alarm can be
created by using both the Shallow and Deep Alarms. If
the Shallow and the Deep alarm bars on the left side of
the display are “overlapped” (that is the Shallow Alarm
bar overlaps the Deep Alarm bar) a new Zone Alarm
will result and be displayed. When the Zone Alarm is
activated, the Twinscope will sound a medium speed
beeping.

Press the "CLEAR" soft key to clear the alarm or
alarms you previously set. Press "CLEAR" in the main
alarm menu to clear all alarms in this view
simultaneously, or press "CLEAR" in the sub-menus to
clear the selected Shallow or Deep Alarm.

31

NORM

NORM

Sector Width & Steer Adjustment

The large rotary knob can be used to both adjust the beam
scanning width and the direction of the scanning sector.
For example, you may not want to scan the full 90 degree
sector from the surface ahead to beneath the boat, but
instead only to scan from the surface ahead to a certain
depth below the surface.

Press the soft key labeled "BEAM" to bring up a sub­menu of beam adjustment choices. By pressing the soft
key labeled "WIDTH", the rotary knob can be used to
adjust the scanning sector width. The actual sector size
will be shown on the display as the BEAM width is
adjusted.

By pressing the soft key labeled “STEER” the resulting
sector can then be steered throughout the possible 90
degree sector (from directly beneath the boat to the
surface ahead).

The RESET button can be used to quickly select three
popular scanning sectors. If the RESET button is pressed
once, the Twinscope will return to the full 90 degree
sector scan (from straight ahead to below the boat),
pressing RESET again will put the Twinscope into one
of three far forward sector scans (each sector is
approximately 12 degres wide).

NORM

NORM

RESET

FULL SECTOR
SCAN

RESET

FAR FORWARD
SECTOR SCANS

Beam Speed (Resolution)

In its normal scanning mode “NORM”, the Twinscope
will send out 50 forward beams and will alternate
between a forward beam and the down-looking beam. In
the “FAST” position, only 30 beams will be used and the
Twinscope will send 5 forward scanning beams for every
down-looking sample. In the “DETAIL” mode, the
Twinscope sends out 90 beams, one every 1 degree for
the maximum resolution, but also at the slowest speed. In
the FAST mode, the picture will have less resolution than
in the DETAIL mode.

32

Plot (Track Plot) View

If your separate Loran C, Decca or GPS receiver has the
proper NMEA #0183 output capability, or if you own the

Interphase Star Pilot GPS, Pilot GPS or Interphase
Pilot Loran, you can easily interface the unit to the
Twinscope to show both digital and graphic navigation

information. Possible information obtained from a
navigation receiver can include track plotting and digital
Lat/Lon readings. The Twinscope can also mark
positions with several different graphic symbols. These
functions will not work unless you are able to
successfully interface a navigational instrument such as a
Loran C, Decca or GPS receiver to the Twinscope. (see
page 66)

From the Command Center select the "Plot View" and
press the "GO" soft key to bring up the menu showing the
features and adjustments for this view.

Range

The "RANGE" soft key calls up the sub-menu which lets
you turn on and off an automatic plot ranging function by
pressing the soft key labeled "TRACK". This feature
will, for example, automatically increase the track plot
range if your position goes off the screen. You can
manually adjust the plotter range by using the "RANGE"
up/down soft keys in this sub-menu.

The Track Plot square on the display shows the current
plotter range (1/4, 1/2, 1, 2, 4, 8, 16, 32, 64, 128) in
statute (U.S.) or nautical miles, depending on the units of
measure selected.

Mark

Pressing the "MARK" soft key allows you to mark your
current position on the track plot screen with one of three
graphic icons - an anchor, a fish or a flag. Each icon can
be used up to ten times on a track plot for a total of 30
possible marks. When power is removed from the
Twinscope, the marks are erased.

33

Center

By pressing the "CENTER" soft key, your current
position will be moved to the center of the track plot
display and the track line dots will be shifted accordingly.

Reset

The "RESET" soft key in the menu restarts your track
plotting by placing your present position in the center of
the track plot screen and erasing all track line dots.

Note: The Twinscope has both a full screen and a split
screen track plotter. Both of these Views are updated
automatically, regardless of what display screen is in use.
Although these two track plot views are similar, the user
may select different ranges for each of these views. For
example, the full screen track plotter can be set up for a
64 mile range, while the split screen track plotter can be
set up for 1/4 mile! This allows you to get two different
instantaneous views of your boat’s movement by
selecting the two different track plot views.

Track Plotter Symbols

+ Starting Position

W Waypoint selected in

navigation receiver

+ Center of plot screen

34

Chart View

(Conventional down looking)

The Twinscope’s phased array transducer can be
electronically steered to look directly below the boat. In
this mode the Twinscope LCD display will show a
picture exactly like conventional fixed beam down­looking fish finders. When in this mode, the Twinscope
offers a full range of sophisticated features which are
found on advanced conventional depth sounders, such as
split screen zoom, bottom lock, fish and depth alarms,
bottom hardness (white-line), plus several other advanced
features.

From the Command Center select the "CHART" View
and press the "GO" soft key to bring up the menu
showing the features and adjustments for this view. The
display should be similar to that at right.

Range Adjustment

Press the button labeled "RANGE" to bring up the Range
Adjustment soft key menu. Press the button labeled
"AUTO" if you would like the Twinscope’s internal
microprocessor to automatically select and adjust the
depth range as bottom conditions change. To manually
adjust the depth, rotate the front panel knob or press
either the range button labeled "∩" or "∪". If you make a
manual depth adjustment, the AUTO range mode is
turned off and will remain off until the button labeled
AUTO is again selected. Note: when in the AUTO
mode, the soft key labeled "AUTO" will be shown in
reverse video (white on black). To return to the main
forward looking menu, press the soft key labeled
"LAST". (To return to the Control Center press the soft
key labeled "MENU")

Sensitivity Adjustment

Press the soft key labeled "SENS." to bring up the
choices available for adjusting the Twinscope's receiver
sensitivity. Press the button labeled "AUTO" so that the
word AUTO is shown in reverse video (white letters on a
black background) if you would like the Twinscope to
automatically adjust its sensitivity for changing
conditions. To manually adjust the sensitivity, rotate the
front panel knob or press the button labeled“- Sens.” or
“Sens.+” to increase or decrease the receiver gain. Note
that the soft key shows a number which indicates the
relative sensitivity being used (+1 to +32). When you

35

choose to manually adjust the sensitivity, the Twinscope
turns off the AUTO sensitivity mode and it will remain
off until the AUTO soft key is again selected. Note:
when AUTO mode is turned on the word will be
displayed in reverse video (white letters on a black
background). To exit the sensitivity menu and save your
adjustments simply press the soft key labeled “LAST” to
return to the main forward looking menu.

Hardness (White-Line)

If the softkey labeled “HARD” is pressed, the display
will show the bottom as a thin line separated by a shaded
area. This mode can be used to find detail close to the
bottom or to indicate the bottom composition. The
thinner the shaded area the softer the bottom. A thick
shaded area indicates a hard or rocky bottom.

Alarm Adjustment

In the forward looking display or view, alarms may be set
for targets which are shallower than, deeper than, or
within a specific zone of adjustable depth settings.

To adjust or clear the alarm settings, press the soft key
labeled “ALARM” to bring up the alarm menu choices.
Pressing the "Deep" or "Shal." soft keys brings up sub­menus to set, adjust or clear the Shallow, Deep and Zone
Alarms. As either the “∩” or “∪” keys are pressed and
held down, or the front panel knob is rotated, a vertical
bar on the left side of the screen (just below the boat icon)
shows the area covered by the depth alarm. Whenever a
solidly displayed target appears within the depth range
covered by the alarm bar, the audible alarm sounds to
warn you of underwater targets or changing bottom
conditions.

NOTE: The FISH Alarm is activated and
cleared independant of other alarms.
When activated, the softkey labeled
“FISH” will be shown in reverse video
(white on black). Press the softkey again to
clear the FISH Alarm

The Shallow Alarm is often used to alert the user to

shallowing bottom conditions and the presence of
underwater targets such as fish. The Deep Alarm is often
used in conjunction with the Shallow Alarm to define a
depth range. If the depth becomes less or greater than the
alarm settings, the audio alarm will sound as a warning.
A Zone Alarm can be created by using both the Shallow
and Deep Alarms. If the Shallow and the Deep alarm
bars on the left side of the display are “overlapped” (that
is, the Shallow Alarm bar overlaps the Deep Alarm bar) a
new Zone Alarm will result and be displayed.

Pressing the “FISH” softkey activates the fish alarm.
This alarm will activate when the unit detects suspended

36

returns that it interprets as fish. Press FISH again to
deavtivate the fish alarm. Note: The fish alarm is an
independant alarm and will not be deactivated by pressing
CLEAR as described below.

Press the "CLEAR" soft key to clear the alarm or alarms
you previously set. Press "CLEAR" in the main alarm
menu to clear all alarms simultaneously, or press
"CLEAR" in the sub-menus to clear the selected Shallow
or Deep Alarm.

Other Features

Press the soft key labeled "OTHER" to bring up a sub­menu that will allow you to create a split screen zoom or
bottom locked picture, have the Twinscope interpret the
display and show fish symbols or adjust the display
scrolling speed.

Zoom & Bottom Track & Bottom Lock
(Split Screen displays)

When using the Chart display , the Twinscope can also
display a split screen high resolution zoom of any 25% of
the depth range, or can show a split screen Bottom Track
or Bottom Lock display. The high resolution Zoom is
very useful when looking for extra detail on the bottom or
in areas above the bottom. Because the Twinscope uses
an Interphase unique 4X over-sampling technique, the
zoom actually shows more data than the non-zoomed
picture. Fishermen have long used the bottom locking
features when fishing over a rocky bottom or when fishing
in rough surface conditions. In the Bottom Track mode,
a zoomed view of the bottom is shown on the left side of
the split screen display. Regardless of changes in bottom
depth, the left side tracks it and keeps the zoomed bottom
picture in view. In the Bottom Lock mode, the bottom is
forced to appear as a straight horizontal line across the
bottom of the left side of the LCD while any targets close
to the bottom are displayed above the bottom line. Over
rough bottoms or in rough conditions, this feature is
extremely useful to eliminate rapidly changing bottom
depths from the display and to show only suspended
targets close to the bottom.

Zoom Bar

Split Screen Zoom Display

Press the soft key labeled "ZOOM ∩∩" to activate the split
screen high resolution zoom function. The left side of the
LCD screen now shows the zoomed area, while the right
side continues to show the conventional depth display.
Hold down the "ZOOM ∪∪" soft key (or rotate the front

Split Screen Bottom Tracking Display

37

Split Screen Bottom Lock Display

Zoomed Display with Fish Symbols ON

panel knob) and notice the vertical bar moving downward
in the center of the display which shows the depth area
that is being “zoomed”. By using the "ZOOM ∩∩" and
"ZOOM ∪∪" soft keys, you can zoom in on particular
depth areas. The Zoom feature expands any 25% section
of the current depth range on the left half of the screen, or
effectively magnifies the section selected by the zoom bar
by 400%.

If you move the zoom bar all the way to the bottom of the
display, the Bottom Track and the Bottom Lock
features can be activated.. When the Bottom Track
feature is activated, the Zoom Bar changes to a thin bar
extending from the top to the bottom of the display.
Pressing the “ZOOM ∪∪” button once more activates the
Bottom Lock feature. When in Bottom Lock, the Zoom
Bar changes to a thick vertical line extending from the top
to the bottom of this display. Move the zoom bar up to
return to the regular zoom operation and turn Bottom
Lock off. Moving the zoom bar all the way to the top of
the display turns the Zoom off and returns you to full
screen bottom history.

Fish Symbol (Turn on/off)

Pressing the soft key labeled "FISH" turns the fish
symbol on or off. When turned on, the "FISH" soft key
will be shown in reverse video and the Twinscope’s
microprocessor will scan the output of the receiver and
looks for specific patterns which it has been programmed
to recognize as fish. If it thinks it “sees” a fish, it creates
a fish symbol in place of the normal blob or arch. Press
the "FISH" soft key to turn this feature off.

Display Scrolling Speed Adjustment

Pressing the button shown as "SCROLL" will change the
speed at which the display moves from right to left
(scrolls). The display scrolling rate will change each time
you press this soft key from: FAST, SLOW or STOP.
Faster scrolling rates are generally used when you want to
see the maximum detail possible while slower speeds are
used when you want to slow the display to show the
maximum amount of bottom history.

38

Data View

From the Control Center, press the soft key labeled
"DATA" to see a split screen display with large digits on
the left and a forward scanning view on the right. The large
digits show the digital depth and, if your Twinscope is
equipped with the optional speed/temperature transducer,
the boat speed, surface water temperature, and distance
traveled log.

Range Adjustment

Press the button labeled "RANGE" to bring up the Range
Adjustment soft key menu. Press the button labeled
"AUTO" if you would like the Twinscope’s internal
microprocessor to automatically select and adjust the depth
range as bottom conditions change. To manually adjust the
depth, rotate the front panel knob or press either the range
buttons labeled "∩" or "∪" or rotate the front panel knob. If
you make a manual depth adjustment, the AUTO range
mode is turned off and will remain off until the button
labeled AUTO is again selected. Note: when in the AUTO
mode, the soft key labeled "AUTO" will be shown in
reverse video (white on black). To return to the main
forward looking menu, press the soft key labeled "LAST".

Log Res. (Distance log reset)

If your Twinscope is equipped with the optional speed/
temperature transducer, the Twinscope will automatically
keep a distance traveled log. You can reset this log to zero
by pressing the "Log Res." soft key.

Note: The Twinscope internal memory keeps the
Twinscope’s distance log data, even when power is
removed. To zero out the distance log, press the softkey
labeled “Log Res.”.

Sensitivity Adjustment

Press the soft key labeled "SENS." to bring up the choices
available for adjusting the Twinscope's receiver
sensitivity. Press the button labeled "AUTO" so that the
word AUTO is shown in reverse video (white letters on a
black background) if you would like the Twinscope to
automatically adjust its sensitivity for changing conditions.
To manually adjust the sensitivity, rotate the front panel
knob or press the button labeled “-Sens” or “Sens+” to
increase or decrease the receiver gain. Note that the soft
key shows a number which indicates the relative sensitivity

39

being used. When you choose to manually adjust the
sensitivity, the Twinscope turns off the AUTO sensitivity
mode and it will remain off until the “AUTO” soft key is
again selected. Note: when AUTO mode is turned on the
word AUTO will be displayed in reverse video (white
letters on a black background). To exit the sensitivity menu
and save your adjustments simply press the soft key labeled
“LAST” to return to the main forward looking menu.
(Press "MENU" to then return to the Control Center).

Alarm Adjustment

In the forward looking display or view, alarms may be set
for targets which are shallower than, deeper than, or within
a specific zone of adjustable depth settings.

To adjust or clear the alarm settings, press the soft key
labeled “ALARM” to bring up the forward looking alarm
menu choices. Pressing the "DEEP" or "SHAL." soft keys
brings up sub-menus to set, adjust or clear the Shallow,
Deep and Zone Alarms. As either the up or down keys are
pressed and held down, or the large knob is rotated, a
vertical bar on the left side of the screen (just below the
boat icon) will move to show the area covered by the depth
alarm. In addition, a horizontal line will appear across the
display. Whenever a solidly displayed target appears at the
same depth as that covered by the alarm bar, the audible
alarm sounds to warn you of underwater targets or changing
bottom conditions. (Note: the horizontal line will
disappear a few seconds after the alarm is adjusted, but the
vertical bar will remain.)

The Shallow Alarm is often used to alert the user to
shallowing bottom conditions and the presence of
underwater targets such as fish, and when activated, will
sound a rapid beeping. The Deep Alarm is often used in
conjunction with the Shallow Alarm to define a depth
range. If the depth becomes less or greater than the alarm
settings, the audio alarm will sound as a warning. If the
Deep alarm is activated, the Twinscope will make a slow
beeping noise. A Zone Alarm can be created by using both
the Shallow and Deep Alarms. If the Shallow and the Deep
alarm bars on the left side of the display are “overlapped”
(that is the Shallow Alarm bar overlaps the Deep Alarm
bar) a new Zone Alarm will result and be displayed. When
the Zone Alarm is activated, the Twinscope will sound a
medium speed beeping.

Press the "CLEAR" soft key to clear the alarm or alarms

you previously set. Press "CLEAR" in the main alarm

40

menu to clear all alarms simultaneously, or press
"CLEAR" in the sub-menus to clear the selected
Shallow or Deep Alarm.

Sector Width & Steer Adjustment

The large front panel rotary knob can be used to both
adjust the beam scanning width and the direction of the
scan. For example, you may not want to scan the full
90 degree sector from the surface ahead to beneath the
boat, but instead only to scan from the surface ahead to
a certain depth below the surface. Press the soft key
labeled "BEAM" to bring up a sub-menu of beam
adjustment choices.

By pressing the soft key labeled "WIDTH", the front
panel knob can be used to adjust the scanning sector
width. The actual sector size will be shown on the
display as the BEAM width is adjusted.

By pressing the soft key labeled “STEER”, the
resulting sector can then be steered throughout the
possible 90 degree sector (from directly beneath the
boat to the surface ahead).

The “RESET” button can be used to quickly select
three popular scanning sectors. If the “RESET” button
is pressed once, the Twinscope will return to the full
90 degree sector scan (from straight ahead to below the
boat), pressing “RESET” again will put the
Twinscope into a far forward scan and pressing it a
third time will set select another far forward scan.
Each of the far forward scans is approximately 12
degrees wide.

RESET

(Full Sector Scans)

Beam Speed (Resolution)

In its normal scanning mode “NORM”, the
Twinscope will send out 50 forward beams and will

alternate between a forward beam and the down­looking beam. In the “FAST” position, only 30 beams
will be used and the Twinscope will send 5 forward
scanning beams for every down-looking sample. In the
“DETAIL” mode, the Twinscope sends out 90 beams,
one every 1 degree for the maximum resolution, but
also at the slowest speed.

RESET

(Far Forward
Sector Scans)

41

Chart/Plot View (split screen)

In this view, the Twinscope shows a split screen display
with a conventional down looking depth sounder picture
on the left and a track plot display on the right. Pressing
the "GO" soft key will bring up a sub-menu to allow
adjustments to the track plotter display. Adjustments to
the left side of the display are not possible in this view.
To make adjustments to the depth ranges, alarms, etc., go
to the CHART view.

From the Command Center select the PLOT/CHART
view and press the "GO" soft key to bring up the menu
showing the features and adjustments for this view.

Range

The "RANGE" soft key calls up the sub-menu which lets
you turn on and off an automatic plot ranging function by
pressing the soft key labeled "TRACK". This feature
will, for example, automatically increase the track plot
range if your position goes off the screen. You can
manually adjust the plotter range by using the Range up/
down soft keys in this sub-menu.

The Track Plot square on the display shows the current
plotter range (1/4, 1/2, 1, 2, 4, 8, 16, 32, 64, 128) in
statute (U.S.) or nautical miles depending on your units of
measure selected.

Mark

Pressing the "MARK" soft key allows you to mark your
current position on the track plot screen with one of three
graphic icons - an anchor, a fish or a flag. You may use
each icon up to ten times on a track plot for a total of up
to 30 possible marks. All Marks are lost when the unit is
turned off.

42

Center

By pressing the "CENTER" soft key, your current

position will be moved to the center of the track plot
display and the track line dots will be shifted
accordingly.

Reset

The "RESET" soft key in the menu restarts your track
plotting by placing your present position in the center
of the track plot screen and erasing all track line dots

Note: All other past information, including track
line dots and marks, will be lost when you Reset the
Track Plot.

Note: The Twinscope has both a full screen and a split

screen track plotter. Both of these Views are updated
automatically regardless of what display screen is in
use. Although these two track plot views are similar,
the user may select different ranges for each of these
views. For example, the full screen track plotter can be
set up for a 64 mile range, while the split screen track
plotter can be set up for 1/4 mile! This allows you to
get two different views of your boat’s movement by
selecting the two different track plot views.

Track Plotter Symbols

+ Starting Position

W Way point selected in

navigation receiver

+ Center of plot screen

43

Chart/Scan View (split screen)

In this split screen view, the Twinscope shows a forward
looking view on the right and a conventional down
looking chart view on the left. In this view, adjustments
can be made to the right side of the display (forward
looking view) but not to the left side (down looking
display). To make adjustments to the down looking
alarms, etc., go to the CHART view.

Range Adjustment

Press the button labeled "RANGE" to bring up the Range
Adjustment soft key menu. Press the button labeled
"AUTO" if you would like the Twinscope’s internal
microprocessor to automatically select and adjust the
depth and forward range as bottom conditions change.
To manually adjust the range, rotate the front panel knob
or press either the range button labeled "∩" or "∪". If
you make a manual depth range adjustment the AUTO
range mode is turned off and will remain off until the
button labeled AUTO is again selected.

Note: when in the AUTO mode, the soft key labeled
“AUTO” will be shown in reverse video (white on black).
To return to the main forward looking menu, press the
soft key labeled "LAST".

Sensitivity Adjustment

Press the soft key labeled "SENS." to bring up the
choices available for adjusting the Twinscope's receiver
sensitivity. Press the button labeled "AUTO" so that the
word AUTO is shown in reverse video (white letters on a
black background) if you would like the Twinscope to
automatically adjust its sensitivity for changing
conditions. To manually adjust the sensitivity , rotate the
front panel knob or press the button labeled “Sens.+” or
“- Sens” to increase or decrease the receiver gain. Note
that the soft key shows a number which indicates the
relative sensitivity being used. When you choose to
manually adjust the sensitivity, the Twinscope turns off
the AUTO sensitivity mode and it will remain off until
the “AUTO” soft key is again selected.

44

N O R MN O R M

N O R MN O R M

Sector Width & Steer Adjustment

The large front panel rotary knob can be used to both
adjust the sector scanning width and the direction of the
scan. For example, you may not want to scan the full 90
degree sector from the surface ahead to beneath the boat,
but instead only to scan from the surface ahead to a
certain depth below the surface.

Press the soft key labeled “BEAM” to bring up a sub­menu of beam adjustment choices.

By pressing the soft key labeled "WIDTH", the rotary
knob can be used to adjust the scanning sector width.

The actual sector size will be shown on the display
as the BEAM width is adjusted.

By pressing the soft key labeled “STEER”, the resulting
sector can then be steered throughout the possible 90
degree sector (from directly beneath the boat to the
surface ahead).

The “RESET” button can be used to quickly select three
popular scanning sectors. If the “RESET” button is
pressed once, the Twinscope will return to the full 90
degree sector scan (from straight ahead to below the
boat), pressing “RESET” again will put the Twinscope
into a far forward scan and pressing it a third time will set
select another far forward scan. Each of the far forward
scans is approximately 12 degrees wide.

RESET

(Full Sector Scan)

RESET

(Far Forward
Sector Scans)

The “RESET” button cycles through the three possible
scan sectors, as shown at left.

Beam Speed (Resolution)

In it’s normal scanning mode “NORM”, the Twinscope
will send out 50 forward beams and will alternate
between a forward beam and the down-looking beam. In
the “FAST” position, only 30 beams will be used and the
Twinscope will send 5 forward scanning beams for every
down-looking sample. In the “DETAIL” mode, the
Twinscope sends out 90 beams, one every 1 degree for
the maximum resolution, but also at the slowest speed.

45

HORIZONTAL SCAN (SEA SCOUT) CONTROL CENTER FLOW

PLOT View (Track Plot)

FWD View (Forward Scan)

DATA View (Large Digits)

CHART/PLOT View

CHART View (Conventional)

SET-UP View (Languages, etc.)

46

CHART/SCAN View

Set-Up View (Horizontal
Mode)

The Twinscope includes a SET-UP View where the
DEMO program can be activated, the units of measure and

language can be selected and the display contrast can be
adjusted. The Twinscope's internal backup battery will
remember all settings for future use.

From the Control Center press the button below the SET-
UP soft key twice to put the display into the SET-UP
View. Then press the button below the “GO” soft key to
use this view. The display should appear as on the right.

Demo Program

We highly recommend you initially operate the Twinscope
in the DEMO mode to familiarize yourself with the many
advanced features of the Twinscope. When using the SET-
UP view, press the soft key below DEMO and hold for 3
seconds to activate the simulation program. The unit will
automatically cycle through a simulated demonstration of
its many features. At any time, you can press any key to
gain control of the DEMO program to make your own
selections and adjustments. If you do not press any button
for about 45 seconds, the unit will automatically resume
cycling through the different demo features on its own.

The pictures shown in the DEMO mode are representations
of what you might see on your Twinscope. In actual use
the picture you will get can vary significantly depending on
depth, bottom and water conditions, the speed of your boat
and many other factors (see Interpreting The Twinscope’s
Forward Display, page 44).

To exit the DEMO program either turn the Twinscope off
and back on again, or press the “DEMO” soft key again.

Select Units of Measure

The Twinscope starts with the last units of measure
selected. By pressing the button indicated on the display,
you can use the large front panel knob labeled “BEAM” to
choose between U.S., Nautical and Metric units. Rotate the
front panel knob to select (highlight) the type of display
units desired. Once selected, press any button to save your
selection and exit. The current choice is displayed each
time the “UNITS” soft key is pressed.

47

The choices and their settings are as follows:

Feature U.S. Nautical Metric

Depth/Range Feet Fathoms Meters

(Ft.) (Fa) (M)

Water Temp. F F C

(ºF) (ºF) (ºC)

Boat Speed Mi./Hr. Knots Knots

(MPH) (KT) (KT)

Distance Log Miles Naut. Mi Naut.Mi

(Mi) (NMi) (NMi)

Nav. Track Plot Miles Naut. Mi Naut.Mi

(Mi) (NMi) (NMi)

Select Menu Language

The Twinscope allows the selection of 9 operating
languages; English, French, Italian, Spanish, German,
Danish, Finnish, Swedish and Greek may be chosen. To
select the operating language, press the button labeled
LANGUAGE. A display window as shown at right will
pop up on the screen showing the available languages and
the one currently selected. Use the large front panel knob
labeled “BEAM” to change (highlight) the language
selection. Once selected, press any key to save your
selection and exit.

Transducer Alignment

The Twinscope includes a feature that will allow you to
compensate for some transducer installation problems
where the transducer is not pointing straight forward but
instead points off to the right or left of the boat. By
pressing the softkey labeled “ALIGN” an alignment sub­menu appears that shows arrows to the right and left. This
adjustment will force the unit to move the center point of
its horizontal scan up to 15 degrees to the left or the right.
The number in the softkey indicates the number of degrees
of offset from center with negative numbers indicating the
number of degrees offset to the left and positive numbers
refer to offset to the right. A zero number in the softkey
indicates that the Twinscope is not using any offset. If
you feel you need to adjust the transducer alignment left
or right, point the boat toward a piling or other small
object and then adjust the alignment until the object
appears in the center of the screen. Use either the softkeys
or the “BEAM” knob to adjust.

48

Forward View (Full Screen)

While in the Control Center press the far left button until
the sideways arrow is shown in reverse video as shown at
left. This will select a full screen horizontal forward
looking display. At the top right of the screen the current
depth beneath the boat is shown in digital numbers. If the
optional speed/temperature transducer is connected to the
unit, the boat’s speed is displayed just to the left of the
digital depth as shown on the picture above.

The vertical scale at the far left of the display shows the
forward range at the center of the display. In this example,
the outer range ring is 360 feet. A target 1/2 this distance
forward would be located at 180 feet in front of the boat.

The numbers on the outer range ring indicate the bearing
from the bow of the boat. The display will show targets up
to +/- 45 degrees ahead of the boat.

Press the GO button to bring up additional adjustments and
features for this forward looking view. Your display menus
should appear as on the left.

Range Adjustment

Press the button labeled "RANGE" to bring up the Forward
Range Adjustment soft key menu as shown at left. Press
the button labeled "AUTO" if you would like the
Twinscope’s internal microprocessor to automatically
select and adjust the range as bottom conditions change.
To manually adjust the range press either the range button
labeled "∩" or "∪", or rotate the large knob. If you make a
manual depth adjustment, the AUTO range mode is turned
off and will remain off until the button labeled AUTO is
again selected. Note: when in the AUTO mode, the soft
key labeled AUTO will be shown in reverse video (white
on black). To return to the main forward looking menu,
press the left soft key labeled "LAST".

Sensitivity Adjustment

Press the soft key labeled "SENS" (for sensitivity) to bring
up the choices available for adjusting the Twinscope's
receiver sensitivity. Press the button labeled "AUTO" so
that the word AUTO is shown in reverse video (white
letters on a black background) if you would like the
Twinscope to automatically adjust its sensitivity for

49

changing conditions. To manually adjust the sensitivity,
either press the button labeled “Sens.+” or “- Sens” or

rotate the front panel knob. Note that the soft key shows
a number which indicates the relative sensitivity being
used (+1 to +32). When you choose to manually adjust
the sensitivity, the Twinscope turns off the AUTO
sensitivity mode and it will remain off until the AUTO
soft key is again selected. To exit the sensitivity menu
and save your adjustments simply press the soft key
labeled “LAST” to return to the main forward looking
menu.

Although the “AUTO” sensitivity will work well in most
situations, you may often find that you need to adjust the
forward sensitivity manually for the optimum picture.

Alarm Adjustment

In the forward looking display or view, a forward alarm
may be set for targets which are closer than a present
distance.

To adjust or clear the alarm settings, press the soft key
labeled “ALARM” to bring up the forward looking
alarm menu choices. As either the up or down keys are
pressed and held down, or the large knob is rotated
counterclockwise , a horizontal bar will move from the
bottom of the display towards the top. A vertical bar will
also move along the range scale. The horizontal and
vertical bar indicate the alarm range. Any strong target
between the boat (at the bottom of the display) and the
alarm bar will cause the alarm to sound. (Note: the
horizontal line will disappear a few seconds after the
alarm is adjusted, but the vertical bar will remain to
indicate the alarms setting.)

To deactivate the alarm either press the "CLEAR" soft
key to clear the forward alarm, or rotate the control knob
clockwise until the alarm bar disappears at the bottom of
the display.

Beam Width & Steer Adjustment

The large rotary front panel knob can be used to both
adjust the beam scanning sector width and the direction
of the scan. For example, you may only want to scan the
area to the port (left) or starboard (right) side of the boat.

Press the soft key labeled "BEAM" to bring up a sub­menu of beam adjustment choices. By pressing the soft

Horizontal Alarm Bar

Vertical Alarm Indication

50

key labeled "WIDTH", the rotary knob can be used to
adjust the scanning sector width. The actual sector size
will be shown on the display as the BEAM width is
adjusted.

By pressing the soft key labeled “STEER” the resulting
sector can then be steered throughout the possible 90
degree horizontal sector .

The RESET button can be used to quickly select three
popular scanning sectors. If the RESET button is pressed
once, the Twinscope will return to the full 90 degree
horizontal sector scan , pressing RESET again will put
the Twinscope into one of two preprogrammed forward
sector scans.

The RESET button cycles through the possible scan
sectors as shown at left.

Beam Speed (Resolution)

In its normal scanning mode “NORM”, the Twinscope
will send out 50 forward beams and will alternate
between a forward beam and the down-looking beam. In
the “FAST” position, only 30 beams will be used and the
Twinscope will send 5 forward scanning beams for every
down-looking sample. In the “DETAIL” mode, the
Twinscope sends out 90 beams, one every 1 degree for
the maximum resolution, but also at the slowest speed.

RESET

FULL SECTOR
SCAN

RESET

FORWARD
SECTOR SCANS

51

Plot (Track Plot) View

If your separate Loran C, Decca or GPS receiver has
the proper NMEA version #0183 output capability,
or if you own the Interphase Star Pilot GPS, Pilot
GPS or Interphase Pilot Loran, you can easily
interface the unit to the Twinscope to show both
digital and graphic navigation information. Possible
information obtained from a navigation receiver can
include track plotting, digital Lat/Lon readings,
course and distance to way points. The Twinscope
can also instantly mark positions with several
different graphic symbols. These functions will not
work unless you are able to successfully interface a
navigational instrument such as a Loran C, Decca or
GPS receiver to the Twinscope.

From the Command Center select the "Plot View"
and press the "GO" soft key to bring up the menu
showing the features and adjustments for this view.

Range

The "RANGE" soft key calls up the sub-menu which
lets you turn on and off an automatic plot ranging
function by pressing the soft key labeled "TRACK".
This feature will, for example, automatically increase
the track plot range if your position goes off the
screen. You can manually adjust the plotter range by
using the "Range" up/down soft keys in this sub­menu.

The Track Plot square on the display shows the
current plotter range (1/4, 1/2, 1, 2, 4, 8, 16, 32, 64,

128) in statute (U.S.) or nautical miles, depending on
the units of measurement selected.

Mark

Pressing the "MARK" soft key allows you to mark
your current position on the track plot screen with
one of three graphic icons - an anchor, a fish or a
flag. Each icon can be used up to ten times on a track
plot for a total of 30 possible marks. When power is
removed from the Twinscope, the marks are erased.

52

Center

By pressing the "CENTER" soft key, your current
position will be moved to the center of the track plot
display and the track line dots will be shifted accordingly.

Reset

The "RESET" soft key in the menu restarts your track
plotting by placing your present position in the center of
the track plot screen and erasing all track line dots.

Note: The Twinscope has both a full screen and a split
screen track plotter. Both of these Views are updated
automatically, regardless of what display screen is in use.
Although these two track plot views are similar, the user
may select different ranges for each of these views. For
example, the full screen track plotter can be set up for a
64 mile range, while the split screen track plotter can be
set up for 1/4 mile! This allows you to get two different
instantaneous views of your boat’s movement by
selecting the two different track plot views. For example,
you could select the range of 64 miles for the full screen
to show far off waypoints, etc., but select a range of only
1/4 mile on the split screen track plotter to show more
detail of your boat’s movement.

Track Plotter Symbols

+ Starting Position

W Waypoint selected in

navigation receiver

+ Center of plot screen

53

Chart View

(Conventional down looking)

The Twinscope’s phased array transducer can be
electronically steered to look directly below the boat.
In this mode the Twinscope LCD display will show a
picture exactly like conventional fixed beam down­looking fish finders. When in this mode, the
Twinscope offers a full range of sophisticated
features which are found on advanced conventional
depth sounders, such as split screen zoom, bottom
lock, fish and depth alarms, bottom hardness (white­line), plus several other advanced features.

From the Command Center select the "CHART"
View and press the "GO" soft key to bring up the
menu showing the features and adjustments for this
view. The display should be similar to that at right.

Range Adjustment

Press the button labeled "RANGE" to bring up the
Range Adjustment soft key menu. Press the button
labeled "AUTO" if you would like the Twinscope’s
internal microprocessor to automatically select and
adjust the depth range as bottom conditions change.
To manually adjust the depth, rotate the front panel
knob or press either the range button labeled "∩" or
"∪". If you make a manual depth adjustment, the
AUTO range mode is turned off and will remain off
until the button labeled AUTO is again selected.
Note: when in the AUTO mode, the soft key labeled
"AUTO" will be shown in reverse video (white on
black). To return to the main forward looking menu,
press the soft key labeled "LAST". (To return to the

Control Center press the soft key labeled "MENU")

Sensitivity Adjustment

Press the soft key labeled "SENS." to bring up the
choices available for adjusting the Twinscope's
receiver sensitivity. Press the button labeled "AUTO"
so that the word AUTO is shown in reverse video
(white letters on a black background) if you would
like the Twinscope to automatically adjust its
sensitivity for changing conditions. To manually
adjust the sensitivity, rotate the front panel knob or
press the button labeled“- Sens.” or “Sens +” to
increase or decrease the receiver gain. Note that the
soft key shows a number which indicates the relative
sensitivity being used (+1 to +32). When you choose

54

to manually adjust the sensitivity, the Twinscope turns
off the AUTO sensitivity mode and it will remain off
until the AUTO soft key is again selected. Note: when
AUTO mode is turned on, the word will be displayed in
reverse video (white letters on a black background). To
exit the sensitivity menu and save your adjustments,
simply press the soft key labeled “LAST” to return to the
main forward looking menu.

Hardness (White-Line)

If the softkey labeled “HARD” is pressed, the display
will show the bottom as a thin line separated by a shaded
area. This mode can be used to find detail close to the
bottom or to indicate the bottom composition. A thick
shaded line indicates a hard or rocky bottom and a thin
shaded line indicates a softer bottom.

Alarm Adjustment

In the forward looking display or view, alarms may be set
for targets which are shallower than, deeper than, or
within a specific zone of adjustable depth settings.

To adjust or clear the alarm settings, press the soft key
labeled “ALARM” to bring up the forward looking
Alarm menu choices. Pressing the "Deep" or "Shal." soft
keys brings up sub-menus to set, adjust or clear the
alarms. As either the “∩” or “∪” keys are pressed and
held down, or the front panel knob is rotated, a vertical
bar on the left side of the screen (just below the boat icon)
shows the area covered by the depth alarm. Whenever a
solidly displayed target appears at the same depth as that
covered by the alarm bar, the audible alarm sounds to
warn you of underwater targets or changing bottom
conditions.

NOTE: The FISH Alarm is activated and
cleared independant of other alarms.
When activated, the softkey labeled
“FISH” will be shown in reverse video
(white on black). Press the softkey again to
clear the FISH Alarm

The Shallow Alarm is often used to alert the user to

shallowing bottom conditions and the presence of under­water targets such as fish. The Deep Alarm is often used
in conjunction with the Shallow Alarm to define a depth
range. If the depth becomes less or greater than the alarm
settings, the audio alarm will sound as a warning. A Zone
Alarm can be created by using both the Shallow and Deep
Alarms. If the Shallow and the Deep alarm bars on the
left side of the display are overlapped (that is, the Shallow
Alarm bar overlaps the Deep Alarm bar) a new Zone
Alarm will result and be displayed. Press the "CLEAR"
soft key to clear the alarm or alarms you previously set.
Press "CLEAR" in the main alarm menu to clear all
alarms simultaneously, or press "CLEAR" in the sub­menus to clear the selected Shallow or Deep Alarm.

55

Other Features

Press the soft key labeled "OTHER" to bring up a sub­menu that will allow you to create a split screen zoom or
bottom locked picture, have the Twinscope interpret the
display and show fish symbols or adjust the display
scrolling speed.

Zoom & Bottom Track & Bottom Lock
(Split Screen displays)

When using the Chart display (conventional down
looking view), the Twinscope can also display a split
screen high resolution zoom of any 25% of the depth
range, or can show a split screen Bottom Track or
Bottom Lock display. The high resolution Zoom is
very useful when looking for extra detail on the bottom
or in areas above the bottom. Because the Twinscope
uses an Interphase unique 4X over-sampling technique,
the zoom actually shows more data than the non­zoomed picture. Fishermen have long used the bottom
locking features when fishing over a rocky bottom or
when fishing in rough surface conditions. In the
Bottom Track mode, a zoomed view of the bottom is
shown on the left side of the split screen display.
Regardless of changes in bottom depth, the left side
tracks it and keeps the zoomed bottom picture in view.
In the Bottom Lock mode, the bottom is forced to
appear as a straight horizontal line across the bottom of
the left side of the LCD while any targets close to the
bottom are displayed above the bottom line. Over rough
bottoms or in rough conditions, this feature is extremely
useful to eliminate rapidly changing bottom depths from
the display and to show only suspended targets close to
the bottom.

Zoom Bar

Split Screen Zoom Display

Press the soft key labeled "ZOOM ∩∩" to activate the
split screen high resolution zoom function. The left side
of the LCD screen now shows the zoomed area, while
the right side continues to show the conventional depth
display. Hold down the "ZOOM ∪∪" soft key (or rotate
the front panel knob) and notice the vertical bar moving
downward in the center of the display which shows the
depth area that is being “zoomed”. By using the
"ZOOM ∩∩" and "ZOOM ∪∪" soft keys, you can zoom in
on particular depth areas. The Zoom feature expands
any 25% section of the current depth range on the left
half of the screen, or effectively magnifies the section
selected by the zoom bar by 400%.

Split Screen Bottom Tracking Display

56

Split Screen Bottom Lock Display

If you move the zoom bar all the way to the bottom of the
display, the Bottom Track and the Bottom Lock
features can be activated.. When the Bottom Track
feature is activated, the Zoom Bar changes to a thin bar
extending from the top to the bottom of the display.
Pressing the “ZOOM ∪∪” button once more activates the
Bottom Lock feature. When in Bottom Lock, the Zoom
Bar changes to a thick vertical line extending from the top
to the bottom of this display. Move the zoom bar up to
return to the regular zoom operation and turn Bottom
Lock off. Moving the zoom bar all the way to the top of
the display turns the Zoom off and returns you to full
screen bottom history.

Fish Symbol (Turn on/off)

Pressing the soft key labeled "FISH" turns the fish
symbol on or off. When turned on, the "FISH" soft key
will be shown in reverse video and the Twinscope’s
microprocessor will scan the output of the receiver and
looks for specific patterns which it has been programmed
to recognize as fish. If it thinks it “sees” a fish, it creates
a fish symbol in place of the normal blob or arch. Press
the "FISH" soft key to turn this feature off.

Zoomed Display with Fish Symbols ON

Screen Scroll Speed

Display Scrolling Speed Adjustment

The second softkey from the right can be used to adjust
the speed of the display. The display “scrolls” the picture
from right to left and this softkey can be used to choose a
scroll speed of “FAST, SLOW, or STOP”. Faster
scrolling rates are generally used when you want to see
the maximum detail possible while slower speeds are used
when you want to slow the display to show the maximum
amount of bottom history.

57

Data View

From the Control Center, press the soft key labeled
"DATA" to see a split screen display with large
digits on the left and a forward scanning view on the
right. The large numbers show the digital depth
and, if your Twinscope is equipped with the
optional speed/temperature transducer, the boat
speed, surface water temperature, and distance
traveled log.

Range Adjustment

Press the button labeled "RANGE" to bring up the
Range Adjustment soft key menu. Press the button
labeled "AUTO" if you would like the Twinscope’s
internal microprocessor to automatically select and
adjust the depth range as bottom conditions change.
To manually adjust the depth, press either the range
buttons labeled "∩" or "∪" or rotate the front panel
knob. If you make a manual depth adjustment, the
AUTO range mode is turned off and will remain
off until the button labeled AUTO is again selected.
Note: when in the AUTO mode, the soft key
labeled "AUTO" will be shown in reverse video
(white on black). To return to the main forward
looking menu, press the soft key labeled "LAST".

Log Res. (Distance log reset)

If your Twinscope is equipped with the optional
speed/temperature transducer, the Twinscope will
automatically keep a distance traveled log. You can
reset this log to zero by pressing the "Log Res." soft
key.

Note: The Twinscope internal memory keeps the
Twinscope’s distance log data, even when power
is removed. To zero out the distance log, press
the softkey labeled “Log Res.”.

Sensitivity Adjustment

Press the soft key labeled "SENS." (for sensitivity)
to bring up the choices available for adjusting the
Twinscope's receiver sensitivity. Press the button
labeled "AUTO" so that the word AUTO is shown
in reverse video (white letters on a black
background) if you would like the Twinscope to
automatically adjust its sensitivity for changing

58

conditions. To manually adjust the sensitivity press the
button labeled “- Sens.” or “ Sens +” to increase or
decrease the receiver gain. Note that the soft key shows a
number which indicates the relative sensitivity being
used. When you choose to manually adjust the
sensitivity, the Twinscope turns off the AUTO
sensitivity mode and it will remain off until the “AUTO”
soft key is again selected. Note: when AUTO mode is
turned on the word AUTO will be displayed in reverse
video (white letters on a black background). To exit the
sensitivity menu and save your adjustments simply press
the soft key labeled “LAST” to return to the main
forward looking menu. (Press "MENU" to then return to
the Control Center).

Alarm Adjustment

In the forward looking display or view, a forward alarm
may be set for targets which are closer than a present
distance.

To adjust or clear the alarm settings, press the soft key
labeled “ALARM” to bring up the forward looking
alarm menu choices. As either the up or down keys are
pressed and held down, or the large knob is rotated
counterclockwise, a horizontal bar will move from the
bottom of the display towards the top. A vertical bar will
also move along the range scale. The horizontal and
vertical bar indicate the alarm range. Any strong target
between the boat (at the bottom of the display) and the
alarm bar will cause the alarm to sound. (Note: the
horizontal line will disappear a few seconds after the
alarm is adjusted, but the vertical bar will remain to
indicate the alarms setting.)

To deactivate the alarm either press the "CLEAR" soft
key to clear the forward alarm, or rotate the control knob
clockwise until the alarm bar disappears at the bottom of
the display.

Alarm Indication

59

Beam Width & Steer Adjustment

The large front panel rotary knob can be used to both
adjust the beam scanning sector width and the
direction of the scan. For example, you may only
want to scan the area to the port (left) or starboard
(right) side of the boat.

Press the soft key labeled "BEAM" to bring up a sub­menu of beam adjustment choices. By pressing the
soft key labeled "WIDTH", the rotary knob can be
used to adjust the scanning sector width. The actual
sector size will be shown on the display as the
BEAM width is adjusted.

By pressing the soft key labeled “STEER” the
resulting sector can then be steered throughout the
possible 90 degree horizontal sector .

The RESET button can be used to quickly select
three popular scanning sectors. If the RESET button
is pressed once, the Twinscope will return to the full
90 degree horizontal sector scan , pressing RESET
again will put the Twinscope into one of two
preprogrammed forward sector scans as shown at
right.

Beam Speed (Resolution)

In its normal scanning mode “NORM”, the
Twinscope will send out 50 forward beams and will

alternate between a forward beam and the down­looking beam. In the “FAST” position, only 30
beams will be used and the Twinscope will send 5
forward scanning beams for every down-looking
sample. In the “DETAIL” mode, the Twinscope
sends out 90 beams, one every 1 degree for maximum
resolution, but also at the slowest speed.

RESET

(Full Sector
Scans)

RESET

(Forward
Sector Scans)

60

Chart/Plot View (split screen)

In this view, the Twinscope shows a split screen display
with a conventional down looking depth sounder picture
on the left and a track plot display on the right. Pressing
the "GO" soft key will bring up a sub-menu to allow
adjustments to the track plotter display. Adjustments to
the left side of the display (down looking depth display)
are not possible in this view. To make adjustments to the
depth ranges, alarms, etc., go to the CHART view.

From the Command Center select the PLOT/CHART
view and press the "GO" soft key to bring up the menu
showing the features and adjustments for this view.

Range

The "RANGE" soft key calls up the sub-menu which lets
you turn on and off an automatic plot ranging function by
pressing the soft key labeled "TRACK". This feature
will, for example, automatically increase the track plot
range if your position goes off the screen. You can
manually adjust the plotter range by using the Range up/
down soft keys in this sub-menu.

The Track Plot square on the display shows the current
plotter range (1/4, 1/2, 1, 2, 4, 8, 16, 32, 64, 128) in
statute (U.S.) or nautical miles depending on your units of
measure selected.

Mark

Pressing the "MARK" soft key allows you to mark your
current position on the track plot screen with one of three
graphic icons - an anchor, a fish or a flag. You may use
each icon up to ten times on a track plot for a total of up
to 30 possible marks. Note: Marks are not saved when
the power is turned off!

61

Center

By pressing the "CENTER" soft key, your current

position will be moved to the center of the track plot
display and the track line dots will be shifted
accordingly.

Reset

The "RESET" soft key in the menu restarts your
track plotting by placing your present position in the
center of the track plot screen and erasing all track
line dots

Note: All other past information, including track
line dots and marks, will be lost when you Reset
the Track Plot.

Note: The Twinscope has both a full screen and a

split screen track plotter. Both of these Views are
updated automatically regardless of what display
screen is in use. Although these two track plot views
are similar, the user may select different ranges for
each of these views. For example, the full screen
track plotter can be set up for a 64 mile range, while
the split screen track plotter can be set up for 1/4
mile! This allows you to get two different instant
views of your boat’s movement by selecting the two
different track plot views. For example, you could
select the range of 64 miles for the full screen to
show far off waypoints, etc.; but select a range of
only 1/4 mile on the split screen track plotter to
show more detail of your boat’s movement.

Track Plotter Symbols

+ Starting Position

W Way point selected in

navigation receiver

+ Center of plot screen

62

Chart/Scan View (split screen)

In this split screen view, the Twinscope shows a forward
looking display on the right and a conventional down
looking chart display on the left. In this view,
adjustments can be made to the right side of the display
(forward looking view) but not to the left side. To make
adjustments to the down looking alarms, etc., go to the

CHART view.

Range Adjustment

Press the button labeled "RANGE" to bring up the Range
Adjustment soft key menu. Press the button labeled
"AUTO" if you would like the Twinscope’s internal
microprocessor to automatically select and adjust the
depth and forward range as bottom conditions change.
To manually adjust the depth range, rotate the front panel
knob or press either the range button labeled "∩" or "∪".
If you make a manual range adjustment, the AUTO range
mode is turned off and will remain off until the button
labeled AUTO is again selected. Note: when in the
AUTO mode, the soft key labeled “AUTO” will be
shown in reverse video (white on black). To return to the

main forward looking menu, press the soft key labeled

"LAST".

Sensitivity Adjustment

Press the soft key labeled "SENS." to bring up the
choices available for adjusting the Twinscope's receiver
sensitivity. Press the button labeled "AUTO" so that the
word AUTO is shown in reverse video (white letters on a
black background) if you would like the Twinscope to
automatically adjust its sensitivity for changing
conditions. To manually adjust the sensitivity, rotate the
front panel knob or press the button labeled “Sens.+” or
“- Sens” to increase or decrease the receiver gain. Note
that the soft key shows a number which indicates the
relative sensitivity being used. When you choose to
manually adjust the sensitivity, the Twinscope turns off
the AUTO sensitivity mode and it will remain off until
the “AUTO” soft key is again selected.

Note: when AUTO mode is turned on the word AUTO
will be displayed in reverse video (white letters on a
black background).

63

Alarm Adjustment

In the forward looking display or view, a forward
alarm may be set for targets which are closer than a
present distance.

To adjust or clear the alarm settings, press the soft
key labeled “ALARM” to bring up the forward
looking alarm menu choices. As either the up or
down keys are pressed and held down, or the large
knob is rotated counterclockwise , a horizontal bar
will move from the bottom of the display towards
the top. A vertical bar will also move along the
range scale. The horizontal and vertical bar indicate
the alarm range. Any strong target between the boat
(at the bottom of the display) and the alarm bar will
cause the alarm to sound. (Note: the horizontal line
will disappear a few seconds after the alarm is
adjusted, but the vertical bar will remain to indicate
the alarms setting.)

To deactivate the alarm either press the "CLEAR"
soft key to clear the forward alarm, or rotate the
control knob clockwise until the alarm bar
disappears at the bottom of the display.

64

RESET

(Full Sector Scan)

Sector Width & Steer Adjustment

The large rotary knob labeled “BEAM” can be used to
both adjust the beam scanning sector width and the
direction of the scan. For example, you may only want to
scan the area to the port (left) or starboard (right) side of
the boat.

Press the soft key labeled "BEAM" to bring up a sub­menu of beam adjustment choices. By pressing the soft
key labeled "WIDTH", the rotary "BEAM" knob can be
used to adjust the scanning sector width. The actual
sector size will be shown on the display as the BEAM
width is adjusted.

By pressing the soft key labeled “STEER” the resulting
sector can then be steered throughout the possible 90
degree horizontal sector.

The RESET button can be used to quickly select three
popular scanning sectors. If the RESET button is pressed
once, the Twinscope will return to the full 90 degree
horizontal sector scan , pressing RESET again will put
the Twinscope into one of two preprogrammed forward
sector scans shown at bottom left.

Beam Speed (Resolution)

In its normal scanning mode “NORM”, the Twinscope
will send out 50 forward beams and will alternate
between a forward beam and the down-looking beam. In
the “FAST” position, only 30 beams will be used and the
Twinscope will send 5 forward scanning beams for every
down-looking sample. In the “DETAIL” mode, the
Twinscope sends out 90 beams, one every 1 degree for
the maximum resolution, but also at the slowest speed.

RESET

(Forward
Sector Scans)

65

NMEA 0183 Interface

The Twinscope will accept navigation data from a
separate Loran C, Decca, and GPS receiver in the
NMEA 0183 data format. This interface has been
tested and is verified to work with the Interphase
Pilot GPS but should work with most other GPS
receivers with the proper NMEA output. It features a
unique, fully dedicated microprocessor for the NMEA
0183 data port which provides maximum compatibility
among Loran C, Decca and GPS receivers.

If your equipment conforms to the following NMEA
0183 i nterface protocols, the Twinscope is probably
compatible- BOD, GLL, IMA, WDR, BPI, BWR,
BWC, BER, BEC, GXP, GDP, GOP, GLP, GGA,
RMA, RMB, RMC. Consult your GPS operation
manuals or contact the manufacturer for further
information on interfacing.

The Twinscope needs to be interfaced via the eight­pin jack on the rear panel of the display unit. The pin
connections are shown at right.

Interphase also offers a NMEA 8-Pin Adapter cable
for the Twinscope as shown at right.

For reference, the internal circuity for the Twinscope’s
NMEA input is shown below. This technical
information may be helpful if you have difficulty with
the NMEA connections.

OUTPUT

+5 V

10K

4N26

Rear Panel 3-Pin NMEA Jack

510

DATA+

DATA-

8-PIN NMEA/SPEED&TEMP CONNECTOR

(located on rear of Twinscope)

1 Speed Data
2 +5VDC
3 NMEA Data
4 N/C
5 NMEA Return
6 + Temp
7 - Temp
8 Shield/Ground

View looking at 8-pin female plug which plugs

into the rear of Twinscope.

Data Return

Data In

(pin 5)

(pin 3)

Twinscope 8-pin NMEA ADAPTOR CABLE

WHITE WIRE....... DATA IN

BLACK WIRE....... DATA RETURN

SHIELD.............. NOT USED

NMEA INPUT

8-pin male

1

3

2

8-pin female

1M

NMEA Input Circuit Showing Protective Opto-

Isolator (4N26)

5’ 8-PIN NMEA Cable

510

Part Number 04-1042-000

66

Strong Return from
Up-sloping Bottom

Weak Return From Far-Forward

Strong Return from Wall Far-Forward

Interpreting The Twinscope’s
Forward Vertical (Probe) Display

The Interphase Twinscope provides a display which
shows acoustic echo returns from the underwater area
beneath and ahead of the vessel. The Phased Array
Transducer steers an acoustic beam over an arc which can
be adjusted from approximately 12 to 90 degrees. As the
Twinscope steers the beam to different positions, it
transmits a pulse of energy and then waits a defined
period of time (depending on the range selected) to
receive any return echoes. As the energy from this
acoustic beam strikes underwater objects or the bottom, a
small portion of the energy is reflected as an echo back to
the transducer. When the echo is received at the
transducer, it’s converted into a small electrical signal and
processed for display on the Twinscope’s LCD.

Since the Twinscope knows the direction in which it sent
the transmit pulse and the time it took to receive the
return echo, it can determine the location of the object or
bottom that created the return echo. As the Twinscope
sequentially steps the acoustic beam from the bottom to
the area ahead of the vessel, the LCD display shows a
continuously updated display of the return echoes in their
approximate position in relation to the vessel.

Because the LCD display is only showing the acoustic
echoes that are returned to the transducer, it can not show
forward bottom conditions that are hidden from its field
of view or are hidden due to obstructions in the acoustic
beam’s path through the water. In addition, smooth
bottom conditions far forward of the vessel are difficult to
see as very little of the acoustic energy is reflected back as
an echo. See the diagram at the left.

Bottoms that are rough and rocky or are sloping upwards
will reflect more acoustic energy back to the transducer
and will show up better far-forward of the vessel than
bottoms that are very smooth or slope downward.
However, even though the bottom may be smooth and
does not show up far forward, large obstructions (sea
wall, large rocks, underwater shelves, etc.) will typically
send back strong echoes that can be seen far forward, as
the diagram at left indicates.

67

Distance Forward

Under typical conditions, the Twinscope will show
level or shallowing bottom contours for a distance
forward of between 4X to 6X the depth below the
transducer. Obstructions in the water, such as walls,
mud banks, etc. may be seen at greater distances,
subject to the depth below the transducer and the
1,200 ft. maximum forward range.

Besides the bottom conditions, water conditions will
also affect the Twinscope’s performance. For
example, surface chop, temperature inversion layers
(thermoclines) and muddy water may degrade
performance.

Noise and Sensitivity Adjustments

The Twinscope features an AUTO sensitivity feature
where it continuously adjusts the sensitivity to achieve
the optimum picture quality. The sensitivity can also
be adjusted manually to allow for a reduction in
sensitivity to minimize the effect of screen noise, or to
increase the sensitivity to show weaker targets.

In the forward scanning modes, the sensitivity setting
is especially important as too little sensitivity will
cause a loss of far forward bottom readings and too
much sensitivity will cause an increase in screen noise
and a possible display of unwanted transducer sidelobe
readings.

Display Depicting Forward Range

Approximately 5 X Current Depth

Display Depicting Forward

Range Approximately 8X

Depth

Transducer Sidelobe Effect

The Twinscope’s transducer, like all acoustic
transducers, does not form a perfect beam of acoustic
energy. Some of the acoustic energy is contained in an
area called the sidelobes. In conventional
downlooking depthsounders, the sidelobes create little
problem except to distort the size of the actual beam
angle; however, in scanning sonars they can create
echoes that are not placed on the LCD screen in their
proper position (also known as false echoes).

As the Twinscope sends off its acoustic beam in a
specific direction, it assumes that any return echoes are
within the main beam. However, if the sidelobe
energy (which is not within the main beam) strikes a
large object (i.e. the bottom) and creates a strong
return echo, the Twinscope has no way of knowing
that this “false” echo was not created by the main
beam and will go ahead and show it on the display as
if it was located within the main beam. The most

Transducer

Sidelobes

Main Beam

Sidelobe

Main Beam

False
Echoes

68

“False” Bottom

Receiver Output Signals

Echoes Caused by
Sidelobe Returns.

Sidelobe Echo Desired EchoTransmit Pulse

typical display of the sidelobe echoes appears as an arc
at the same distance as the bottom depth , and in the
worst case, from the bottom below to the surface ahead.
After using the Twinscope in different situations, with
different gain settings, you should become proficient in
identifying the bottom echoes caused by the
transducer’s sidelobes. To minimize the sidelobe
effect, the gain should be reduced.

However, in some situations, you may want to ignore
the sidelobe effect and increase the gain to achieve a
better display of the bottom far-forward of the vessel.

TVG (Time Variable Gain)

As the acoustic signal travels through the water it is
attenuated in strength and also loses strength because
the signal is being spread over a larger and larger area.
For this reason, distant targets appear weaker than
close targets - even if both targets are of identical size.

The Twinscope’s receiver circuit includes a Time
Variable Gain (TVG) feature where the receiver’s gain
is controlled by the microprocessor and increases in
value as the depth or forward range increases. This
feature tends to compensate for the weakening of the
signal at large distances as the receiver’s gain will be
increased as the signal gets smaller. It is also helpful
in minimizing sidelobe problems as shown in the
diagram at left.

Receiver Input Signals

Receiver Gain Level

Receiver Gain (TVG)

Desired Echo

Sidelobe Echo

How Time Varible Gain Helps Reduce Sidelobe

Effects

In the diagram, a boat is shown with the main
transducer beam aimed far forward. However, the
sidelobe beam is also striking the shallow bottom
directly beneath the boat. Both the desired echo (the
one from the far forward beam) and the sidelobe echo
will reach the receiver as shown in the graph just
beneath the boat. Note that the transmit signal, the
sidelobe echo and the desired echo have been
arbitrarily shown as the same size.

The diagram just below shows how the TVG on the
receiver changes with distance (or time). The farther
the target from the boat, the larger the receiver gain.
Finally, the bottom diagram shows the output of the
receiver after amplification with the TVG feature. Note
that the TVG has reduced the sidelobe echo compared
to the desired echo.

69

Interpreting The Twinscope’s
Forward Horizontal (Sea Scout)
Display

In the Horizontal (Sea Scout) mode, the Twinscope scans
from left to right across the boats bow. The forward
scanning elements in the transducer are positioned so that
the plane of the horizontal scan is angled downward
approximately 10-20 degrees from the water’s surface
(see sketch at right). This downward angle is designed to
help reduce the effects of surface noise clutter when the
water is choppy and to allow easier mounting of the
transducer to the transom of smaller boats.

As the acoustic sound beam is projected away from the
boat, the cross-sectional diameter of the beam increases.
At a range of approximately 4 to 5 times the depth of the
water, the sound beam will begin intersecting the bottom
and some of the sound energy that intersects the bottom
will be reflected back and appear on the Twinscope’s
screen as bottom echos.

It is important to understand that the Twinscope will
often see the bottom and show it on the forward display.
This display information can be used to help understand
the structure of the bottom ahead of the boat, but the
bottom echos can also mask or be confused as fish targets.
Several forward display situations with comments are
shown on the following page.

Plane of Forward Scan is Angled 20 Degrees

Downward From Surface. Forward beam will

reach bottom at approx. 3 to 3.5 times the actual

depth of water that you are in.

70

Beam Depth at Various Forward Ranges

Forward

250 500 750

Beam Depth =
Approx. .36 X
Forward
Distance
at 20 Degree

1000

Depth

90

180

270

360

The top picture and resulting screen display shows a boat in
12 feet of water. The Twinscope’s forward range is set to
40 ft. Notice on the scan picture on the right side of the
display, the bottom is just starting to show at about 35 to 40
ft in front. A school of fish or bait is off to the port side of
the vessel at a forward distance of about 14 feet and
additional fish or bait appears directly in front of the boat at
a distance of only a few feet. Also notice the fish or bait
near the bottom on the downlooking mode on the left side of
the display.

In the lower picture and resulting screen display, notice that
even in shallow depths of 12 ft the Twinscope is detecting
targets at a forward distance of approximately 200 feet.
When looking far forward in shallow situations such as this,
it is advisable to adjust the gain manually. Otherwise the
Auto gain feature will reduce the gain because of the strong
close-in bottom reflections.

On the following page, two bottom situations are sketched
along with the resulting Twinscope Display.

Noise and Sensitivity Adjustments

The Twinscope features an AUTO sensitivity feature
where it continuously adjusts the sensitivity to achieve the
optimum picture quality. The sensitivity can also be
adjusted manually to allow for a reduction in sensitivity to
minimize the effect of screen noise, or to increase the
sensitivity to show weaker targets.

In the forward scanning modes, the sensitivity setting is
especially important as too little sensitivity will cause a loss
of target detection and too much sensitivity will cause an
increase in screen noise. In the AUTO mode, the
Twinscope increases the forward gain until there is a certain
density of targets on the display. In most situations the
AUTO gain mode works well, but manual adjustments will
often be required to get the optimum picture - especially
when looking far ahead in shallow water.

40ft Forward Range, Water Depth of 12 Ft

Bait

Bottom

Bait

240ft Forward Range, Bottom Depth of 12 ft.

Fish or Bait

Bottom

71

Examples of two bottom situations, followed by
the resulting view on the Twinscope split­screen Chart/Scan Display.

Bottom Getting
Deeper to port
(left) of boat.

Sides of
Underwater
Trench

Bottom
Under Boat

72

Reference Information

Phased Array Technology

Most existing depthsounders and fishfinders in the marine
market use a mature “fixed beam” technology which was
originally developed during W.W. II to detect the
presence and distance of submarines. Products using this
technology usually have a transducer mounted on the rear
of the vessel, making contact with the water. The
transducer is connected to an electronic display module
which is typically mounted near the boat’s steering
station.

These transducers are typically made up of a
piezoceramic element which is encapsulated in a
hydrodynamically shaped plastic or bronze case. The
piezoceramic element has the important property in that it
will vibrate when shocked with a high voltage electrical
signal and will itself give off a small electrical signal
when physically vibrated. If the display unit sends a large
pulse of voltage down the cable to the transducer, the
transducer will vibrate and the resulting acoustic
vibrations will travel through the water until they strike
an object, such as the bottom or suspended fish. When
striking an object, a small amount of the acoustic energy
is reflected and this “echo” returns and causes a small
vibration in the transducer. The small vibrations in the
transducer caused by the returning acoustic echo cause
the transducer to send a small electrical signal back up the
cable to the display unit. The user can then view the
presence of, and distance to, these underwater objects.

Cable

Display

Transducer
Housing

Ceramic Element

Acoustic Beam

Echo
Bottom

The transducer element, depending on the physical
characteristics of the piezoceramic element (thickness,
diameter, etc.) has a fixed direction in which it is most
efficient at sending and receiving acoustic signals. This
direction is called the “beam angle” and is of critical
concern to most knowledgeable fishermen, as the display
will typically show only those targets that are within this
beam angle. A large beam angle will show targets from a
larger underwater area, but suffers from lack of
resolution. That means that although several targets may
be in the beam angle, the user can only determine their
distance from the transducer, not their lateral position
within the beam. For example, if one fish target is 10’
below the boat at the far right edge of the beam angle, it
will show the same display as if it were 10’ below the
boat at the far left edge of the beam angle. In addition, if
fish are present at exactly the same depth but at different

Beam
Angle

Two Objects
at Same
Depth Will
Appear as
One Object

73

sides of the underwater beam, the transducer will
receive echoes from both fish targets at the same
time and the display will only show a single target.
This is a serious limitation to the conventional
technology.

To get around this limitation, several manufacturers
have resorted to adding more piezoceramic elements
to the transducer, each pointed in a different
direction. By selectively using each piezoceramic
element the transducer has the ability to point or
look in as many different directions as there are
piezoceramic elements. After approximately four
elements, however, the transducer housing starts to
become physically large and cumbersome. To date,
manufacturers have put as many as five separate
elements into the transducer to enable users a view
in up to five different underwater directions. In the
future, Interphase believes that this multiple fixed­beam approach has serious limitations, especially for
use in more advanced products where maximum
underwater coverage and resolution are important.

Three Fixed-Beam System, Looking Down and

to Each Side of Boat

Bottom

Development of New Technology

To get around these limitations and provide a sonar
system that can achieve both outstanding coverage
and good resolution, Interphase pioneered the use
of Ultrasonic Phased Array Technology. In 1991
we received the prestigious IMTEC Innovation
Award in recognition of the importance of this new
technology to the marine industry. Although new to
the sportsfishing and recreational marine industry,
“phased array ultrasound technology” has proven its
capabilities in the medical industry for many years.
The amazing video images provided by medical
ultrasound equipment are familiar to most people
and clearly demonstrate the technology’s ability to
show highly defined images in a real-time or live­action mode. Interphase has taken this same
technology and modified it for use in the marine
market.

An acoustic phased array is a group of piezoceramic
elements that are precisely sized and spaced. Each
element will send and receive acoustic pulses as
when used in the conventional single element
technology. However, when all the elements in the
array are sending or receiving acoustic energy at the
same time, the entire array behaves like a single
larger element with one important difference: the

12º Acoustic Beam Can
Be Steered In Any
Direction Over a 90
Degree Arc.

8 Element
Ceramic
Phased
Array

74

ability for the array to concentrate its acoustic energy in
different directions depending on the different “phasing” of the
signals applied or received by each element. Depending on the
signal phasing to the array, acoustic beams can be directed in
an almost unlimited number of directions. For example, using
two 8 element phased arrays, the Twinscope is capable of
steering the acoustic beam in over 90 different angles in two
directions! Conventional fixed-beam technology would have
required the use of at least 180 transducer elements, each
pointed in a different direction. Such a transducer would be
much too costly and bulky to be of any practical use in the
marine market.

Since the acoustic beam in the phased array is steered
electronically, requiring no moving parts, it can be quickly and
reliably scanned and re-scanned over a large area. When
displayed, the changing information between subsequent scans
takes on an almost animated quality - showing, for example,
the movement of underwater fish or the constantly changing
bottom conditions.

In addition to its ability to electronically steer an acoustic
beam, the phased array has other advantages over fixed beam
technologies such as: allowing the user to adjust the transducer
beam width, to scan large areas limited only by the physics of
speed of sound through water (5,000 ft/sec.), and the ability to
provide nearly real-time or live-action underwater views.

75

FREQUENTLY ASKED
QUESTIONS

What is the difference between the Probe and Sea
Scout scaning modes?

Both the Probe and Sea Scout scan forward of the boat,
but sweep a single beam (12 degree cone angle) in
different directions. In the Probe mode, the beam sweeps
vertically, from the surface to the bottom (directly under
the boat). In the Sea Scout mode the beam sweeps the 12
degree beam from side to side (45 left to 45 right).

Imagine swinging your arm from straight down by your
side, then up pointing at the horizon. You have just
imitated the Probe sweeping pattern.

Now, instead of sweeping your arm up and down, point
your arm at the ground about 12 feet in front of you.
Now sweep your arm from right to left at the same slight
downward angle. You have just imitated the sweeping
pattern of the Sea Scout! The Sea Scout beam angles
down about 10-20 degrees from the transducer (about 25
feet deep for each 100 feet of range).

scanning sonar operates with a 12 degree cone angle
beam. This means that the diameter of the beam at 100'
is about 15' wide. The transducer operates at
approximately 200 kHz. The beam has many unique
characteristics which allow increased resolution as well
as increased ranges.

How powerful (watts) are the Phased Array Sonar
units from Interphase?

Phased Array Sonar does not operate in the same way
that traditional marine sounders work. Interphase has
combined high-tech software with ultrasound technology
from the medical field and newly released military
ultrasound technology. It operates on approximately 400
watts (RMS tested at the transducer or 3,200 watts peak
to peak) but is channeled through eight (8) separate
elements and the signal is phased via our software.

IMPORTANT NOTE: All sonar sounders, if more than
200 watts RMS, have a limited use in shallow water (less
than 10' from transducer to bottom). In most cases, the
need to see forward occurs when traveling from deeper to
shallower depths. Forward scanning is possible but
limited when the water is less than 10' deep. Some clutter
on the screen will occur in shallow environments.

The Probe display will show both bottom and suspended
targets directly in front of the boat. You simply point the
boat where you want to see. The display will show any
targets distance and depth.

The Sea Scout will display suspended targets only, but
will tell you their direction from your boat and their
distance from you. You must estimate the depth of any
targets ahead.

Which one of the scanning modes do I need?

For suspended targets ahead (bait fish, salmon, albacore,
etc.) the desired scanning mode is the Sea Scout.
For both suspended targets and a view of the bottom
ahead (collision avoidance, scuba, bottom fish, search/
rescue, ice fishing) you need the Probe mode.

How wide is the scanning beam?

The phased array scanning beam on all Interphase

76

What type of transducer is needed and what does it
look like?

The transducers for the Twinscope are available in
transom or thru-hull configurations. If you are operating
an inboard, you must use the thru-hull. Remember that
you are measuring ahead from the transducer, therefore,
placing it as far forward as possible will provide you
with greater forward range.

The thru-hull transduces are slightly larger than a tennis
ball and extremely hydrodynamic (they pass through
water in a streamlined fashion).

The transom transducers are mounted on a stainless steel
kick-up bracket in order to minimize the possibility of
damage if striking a floating object. The transom
brackets will 'kick-up' at speeds in excess of 30 knots.
Therefore, if you intend on using the forward scan at high
speed, you should consider a thru-hull transducer.

How far ahead will I be able to see?

In most cases, forward scanning in the Probe mode is
approximately 5 - 6 times farther ahead than the depth of
water. For example, if you are in 15' of water, you can
see about 90' ahead of the transducer. The range is
limited to 1,200' forward and 800' in depth.

Typically, if you are attempting to see great distances
ahead, only targets but not the bottom will appear
beyond 300 feet ahead, because a flat bottom with no
targets (rocks, wrecks, fish, etc.) will be stealth or
invisible to sonar pulses at great distances. A rocky
bottom or approaching hazard will normally show up
clearly on the display, even far ahead.

The Sea Scout mode will provide you with distance and
direction of the targets, but will not provide depth of the
targets, as they may be detected by a pulse that has
actually bounced off of the bottom.

Can I see a regular depth sounder view of the bottom
and scan forward or zoom into the bottom at the same
time?

All Interphase products provide both full screen views as
well as split screens for bottom charting, forward
scanning or zoom view (depending on the unit's
functions), and even Loran/GPS ready track plotting
views.

The most popular display is a split screen with bottom
chart (viewing the bottom as it passes under the boat)
and forward scanning view at the same time. You can
actually see approaching targets and then watch as they
pass under the boat.

Can I get speed and temperature with my Interphase
Sonar or Fishfinder?

All Interphase products are available with speed and
temperature sensors. A separate transducer is required
for speed and temperature input and display. The speed/
temp transducer is available with either thru-hull or
transom mounting.

It is not necessary to use a thru-hull speed/temp
transducer if the scanning transducer is a thru-hull
mount. Speed and temperature transducers can be
placed on a transom, aft of an inboard engine.

77

Maintenance

The Twinscope Forward Scanning Sonar has been designed to provide reliable, trouble-free performance for years.
Follow the maintenance tips below to ensure that your Twinscope remains problem free.

1) Keep your Twinscope clean and dry. Occasionally wipe unit off with a damp cloth, but be careful not to scratch
the lens covering the LCD screen. For stubborn dirt, use a mild soap and a damp cloth. NEVER USE SOLVENTS
SUCH AS PAINT THINNER, ACETONE, OR GASOLINE TO CLEAN YOUR Twinscope.

2) Occasionally clean the face of the depth transducer (sensing surface) and carefully remove any marine growth.
Use a mild detergent, 220 grit sandpaper, or crocus cloth to remove stubborn growth.

3) If the in-line fuse is blown, replace it with a 2 amp fuse. NEVER REPLACE WITH A HIGHER AMP RATING!
If the fuse continues to blow, check the polarity of your 12 VDC power source. If the polarity is correct, check with
the Technical Service Department at [phone], extension 16.

4) In order to protect your transducer from water damage, paint it with one of the following brands: Interlux­UltraCoat, Fiberglass Bottom Coat, Super Bottom Coat; Pettit-UniPoxy; Rule-Super KL, Gloss Dura Poxy. DO

NOT use a solvent based paint.

5) DO NOT allow any solvents, i.e. gasoline, acetone, to come in contact with the transducer or head unit as
these may dissolve the material.

78

Reset & Calibration

FACTORY RESET:

Start with the unit off.

1. Press soft keys #4 and #5 and hold (as labeled in diagram below)

2. Press the #6 key.
The unit will turn on and beep three times, then release the keys. The units logo should appear in the display.
This will reset the unit to it’s ‘factory settings’, please refer to the set-up view portion in the Operations Manual
if changes were previously made to the language or level / alignment.

LCD Display

#1 #2 #3 #4 #5

SPEED CALIBRATION (Log Adjustment):

To adjust the speed calibration perform the following steps: Select the Data View and then Range option.
Press and hold the Log Res. for three seconds to bring up the log/speed adjustment menu. Use the front panel
knob to adjust the calibration factor. The unit will adjust up to 40% either positive or negative from the factory
settings

TRANSOM MOUNT BRACKETS:

The transom mount scanning sonar transducers now come with a stainless steel ‘kick up’ bracket. In some
manuals the reference pictures for mounting the bracket and transducer may refer to a plastic bracket. The
stainless steel brackets include a spray shield to reduce possible ‘rooster tails’. The spray shield rests between
the transducer tabs in a ‘U’ fashion with the notch facing aft.

Product Support:

Monday thru Friday 8:00 AM 5:00 PM PST Phone: [phone] Ext. 16 Fax: [phone]
E-Mail: [e-mail]

#6

79

Troubleshooting Guide

If you are experiencing trouble with your Twinscope, please refer to the following checklist:

PROBLEM SOLUTION

Unit will not turn on. Check fuse, battery voltage and power connections.

Also, check for continuity through the in-line fuse holder.

Unit beeps but no picture appears Check your connections to the battery. Check for
on the screen. corrosion on the battery terminals or on the wiring

connections on a fuse block or buss bar.

Unit blows fuses. Wiring is reversed or there is excessive current from the

battery. The red wire should be “+” (positive) and have
continuity with pin #1 on the female side of the power
supply lead.

Loses picture at speed. Adjust the transducer angle or placement. Make sure that

the transducer is installed in the area which has the least
amount of water turbulence.

LCD darkens in sunlight after Overexposed to sunlight - provide shading for display.
prolonged use.

Screen is full of noise, or has dots Reduce your SENS setting and review the section on
running through it. interference. (see next page)

Bottom slopes up/down Adjust the transducer LEVEL adjustment in SETUP view.

Speed display is erratic. Check and clean the impeller wheel and the surrounding

area - be sure the impeller wheel spins freely.

Digital water depth not working. Increase your SENS, and check that you are in the proper

depth range.

80

Interference Problems

Interference can come from several sources. The most common of these are:

1) Other nearby depth sounders operating at the same frequency.

Interference caused by nearby depth sounders operating on or near the same frequency as the Twinscope will
typically appear as “rabbit tracks” that march up and down the screen. Reducing the gain will help minimize this
problem.

2) Radiated interference from the boat’s electrical system (alternator, distributor and spark plugs) or from nearby
equipment that radiates electrical noise.

Radiated interference caused by the boat’s engine can usually be identified by observing the Twinscope with both

the engine running and turned off. If the interference disappears when the engine is turned off, it is safe to assume
that the engine is the source of the interference.

3) Conducted interference usually occurs when the Twinscope shares a 12VDC power lead with other noisy
equipment (i.e.; bilge pumps, motors, refrigeration systems, autopilots, etc.)

This type of interference can usually be eliminated by using the same techniques used in the automotive industry to

eliminate interference to car radios, CB’s, etc. The following actions may be required:

1) Reduce the SENS setting to minimize interference.

2) Make sure your boat uses resistor type spark plugs and plug wiring.

3) Install a suppressor on the center lead of the distributor.

4) Install an alternator filter to smooth the alternator’s output signal.

Interference may also be caused by radiation from other nearby equipment and can be detected by turning off all other
equipment and observing the Twinscope display as each suspected source is turned back on. This type of
interference can usually be eliminated by moving the Twinscope away from the source and checking to ensure that
the interfering source is properly grounded.

Interference causing the display to be unstable, to pulsate or periodically change size is usually caused when another
piece of equipment shares the same 12 VDC power leads from the battery. This problem is especially severe when
equipment requiring large current surges (i.e.; autopilots, refrigerators, or bilge pumps) share the same power leads.
Minimize this type of interference by running the Twinscope’s 12VDC power leads, or those of the interfering
equipment, directly to the battery.

Alternately, you may find it helpful to install a separate dedicated power supply battery that is used only to run your
electronic gear (e.g.; fishfinders, VHF radios, radar units, etc.). If your unit shuts off during low voltage situations,
such as when cranking your engine starter, you may want to install an isolator switch with an “A/B” type of battery
system. An “A/B” system allows you to run your electronic gear on one battery, while the starter and alternator are
hooked up to the other battery.

Your authorized marine electronics dealer is familiar with the methods of reducing electrical interference and is
qualified to assist you should a problem persist.

81

Specifications

Depth only

Transom Transducers

Part # T1-0200-025

& T1-0200-028

Depth only Single

Thru-Hull Transducer

Part # T1-I200-032

Two Depth-Only

Thru-Hull Transducers

Part # T1-I200-026

T1-I200-029

12 VDC Power

Part # 04-0001-008

Display Type: 128 x 160 pixels; 20,480 total pixel Super Twist LCD
Depth Ranges: 24 overlapping depth ranges, 0 - 20 to 0 - 800 feet
Forward Ranges: 24 overlapping forward ranges, 0 - 30 to 0 - 1,200 feet

Transmit Frequency: 200 kHz
Zoom Ranges: Variable Zoom allows 25% of depth range to be displayed

across the entire screen.

Pulselength and
Sounding Rates: Automatically optimized for selected range.

Transmitter Power: Over 400 watts RMS (3,200 watts peak to peak)
Surface Water Temperature: With optional speed/temperature upgrade kit installed, display

continuously indicates surface water temperature in tenths of a
degree F from 32.0º to 99.9º F.

Power Requirements: 10.5 to 16 VDC, less than 0.5 Amp.
Dimensions: 8”W x 5.5”H x 3.5”D
Standard Equipment: Display unit, 12 VDC power cable with in-line fuse, mounting

bracket with knobs, operation manual, weather cover and depth
transducer with 30’ cables.

Specifications subject to change without notice.

82

Supply Cable

Notes

83

84

How to Obtain Service

If you feel your set is not operating properly, first refer to the sections of this manual on Troubleshooting and
Interference Problems. This information solves the most common problems. If problems persist, please call
Interphase Technical Service at [phone], ext 16 or send your unit in with the information below filled out.

If you do need to return your set, send it to the following address:

Service Department
Interphase Technologies, Inc.
2880 Research Park Drive, Suite 140
Soquel, CA 95073

In addition, to speed your repair please fill out the following, tear this page out of the manual (or photocopy it), and
tape it to your unit for our technicians to review. For fastest warranty service, include a copy of your purchase receipt
to verify the purchase date.

RETURN TO:

(City) (State) (Zip)

(Your Name)

(Street Address - No P.O. Boxes Please)

Daytime Telephone: ( )
Evening Telephone: ( )

Model: Twinscope Serial #:

Purchase Date / /

Type of transducer: Transom mount Thru-Hull Other

Please describe the problems you are having with the unit in as much detail as possible in the space below. Please
use another sheet of paper if necessary.

85

86

Interphase Technologies, Inc.

5 Year Limited Warranty

Any unit that fails during the first year of the warranty period period will, at
Interphase’s option, be repaired or replaced at no charge to the customer
provided it is returned to Interphase, freight prepaid with proof of date of
purchase and a description of the malfunction. Repair or replacement during the
warranty period will not extend the basic warranty period.

From the second through the fifth year, Interphase will, at it’s option, repair or
replace defective units for a fixed fee. This fee will be set at the beginning of
each year. More information about the fixed rate repair fee is available by
calling Interphase at [phone].

This warranty does not apply to an Interphase product that has failed due to
improper installation, misuse, or accident, nor does it apply to products which
have been repaired or altered outside the Interphase factory.

Any costs incurred with transducer replacement are specifically excluded from
this warranty other than the cost of the transducer itself.

This warranty does not include incidental or consequential damages and
Interphase disclaims any liability for any such damages. All implied warranties,
if any, are limited in duration to the above stated one year warranty period.
Some states and provinces do not allow the exclusion or limitation of incidental
or consequential damages, therefore, the above limitations may not apply to you.

The completion and return of the enclosed Warranty Registration Card is a
condition precedent to the warranty coverage.

This warranty gives you specific legal rights which may vary from state to state
and province to province. This warranty is limited only to the original purchaser
of the unit.

87

88