Tyco LBI-38636S User Manual
Installation Manual
LBI-38636S
MASTR® III
Conventional Base Station
LBI-38636S
NOTE
Repairs to this equipment should be made only by an authorized service technician or facility designated by the supplier.
Any repairs, alterations or substitution of recommended parts made by the user to this equipment not approved by the
manufacturer could void the user’s authority to operate the equipment in addition to the manufacturer’s warranty.
NOTICE!
The software contained in this device is copyrighted by M/A-COM Private Radio Systems, Inc. Unpublished rights are
reserved under the copyright laws of the United States.
This manual is published by M/A-COM Private Radio Systems, Inc., without any warranty. Improvements and changes to this manual necessitated by
typographical errors, inaccuracies of current information, or improvements to programs and/or equipment, may be made by M/A-COM Private Radio
Systems, Inc., at any time and without notice. Such changes will be incorporated into new editions of this manual. No part of this manual may be
reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, for any purpose, without the
express written permission of M/A-COM Private Radio Systems, Inc.
Copyright 1992-2002 M/A-COM Private Radio Systems, Inc. All rights reserved.
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LBI-38636S
TABLE OF CONTENTS
Page
PRODUCT SPECIFICATION FOR CE MARKED EQUIPMENT ..................................................................................5
MAXIMUM PERMISSIBLE EXPOSURE (MPE) LIMITS.............................................................................................. 6
DETERMINING MPE RADIUS.................................................................................................................................... 6
SAFETY TRAINING INFORMATION ............................................................................................................................ 6
STATION SPECIFICATIONS (GENERAL).....................................................................................................................8
PUBLICATIONS INDEX .................................................................................................................................................. 9
SAFETY SUMMARY...................................................................................................................................................... 11
GROUND THE EQUIPMENT.....................................................................................................................................11
REPLACEMENT OF PLUG-IN CIRCUIT MODULES .............................................................................................11
ELECTROSTATIC DISCHARGE - SENSITIVE COMPONENTS............................................................................11
DO NOT SUBSTITUTE PARTS OR MODIFY PRODUCT.......................................................................................12
INTRODUCTION ............................................................................................................................................................ 12
CABINET ..................................................................................................................................................................... 12
STATION POWER SUPPLY.......................................................................................................................................12
TRANSMITTER/RECEIVER SHELF......................................................................................................................... 12
TRANSMITTER POWER AMPLIFIER......................................................................................................................12
UNPACKING EQUIPMENT........................................................................................................................................... 12
SITE PREPARATION AND INSTALLATION .............................................................................................................. 12
CABINET INSTALLATION ....................................................................................................................................... 12
Single 37-inch Cabinet Installation...........................................................................................................................12
Double Stacked 37-inch Cabinet installation............................................................................................................13
ELECTRICAL CONNECTIONS.................................................................................................................................14
AC Power..................................................................................................................................................................14
Microphone...............................................................................................................................................................14
Antenna.....................................................................................................................................................................14
TELEPHONE LINE CHARACTERISTICS................................................................................................................ 14
Telephone Lines........................................................................................................................................................ 14
Types Of Voice Grade Lines ....................................................................................................................................14
Tone Remote Control Systems .................................................................................................................................17
Voting System Considerations.................................................................................................................................. 18
Ordering Voice Grade Telephone Lines ................................................................................................................... 18
Telephone Company Ordering Information.............................................................................................................. 19
TELEPHONE LINE INSTALLATION .......................................................................................................................19
DC Remote Installation.............................................................................................................................................19
E & M Signaling ....................................................................................................................................................... 19
Tone Remote Installation..........................................................................................................................................20
STATION SETUP ............................................................................................................................................................ 24
SETUP PROCEDURE..................................................................................................................................................24
ALIGNMENT PROCEDURE ...................................................................................................................................... 26
AUDIO ROUTING AND ADJUSTMENTS.................................................................................................................... 29
TX AUDIO LEVEL ADJUSTMENT...........................................................................................................................29
REMOTE CONTROLLER TO STATION CONTROL PANEL ADJUSTMENTS....................................................39
LINE OUT LEVEL ADJUSTMENT ...........................................................................................................................39
LINE IN LEVEL ADJUSTMENT ...............................................................................................................................39
DSP LEVEL ADJUSTMENTS .................................................................................................................................... 39
REPEATER PANEL INSTALLATION.......................................................................................................................40
CSI Model 32 Repeater Panel...................................................................................................................................40
Zetron 38A Repeater Panel.......................................................................................................................................40
ACCESSORIES................................................................................................................................................................ 42
4
LBI-38636S
ILLUSTRATIONS
Page
Figure 1 - Typical 37-inch MASTR III Stations............................................................................................................... 11
Figure 2 - 37 Inch Mounting Footprint............................................................................................................................. 13
Figure 3 - 37-Inch Cabinet................................................................................................................................................ 13
Figure 4 - Stacked 37-Inch Cabinets 13
Figure 5 - Microphone Connections ................................................................................................................................. 14
Figure 6 - T/R Shelf Connections..................................................................................................................................... 15
Figure 7 - Typical E & M Signaling Application ............................................................................................................. 21
Figure 8 - METHOD 1 (Single Metallic Pair).................................................................................................................. 22
Figure 9 - METHOD 2 (Single Metallic, Earth Ground).................................................................................................. 22
Figure 10 - METHOD 3 (Metallic Control Pair, Audio Pair)........................................................................................... 23
Figure 11 - METHOD 4 (Full Duplex Metallic TX Pair)................................................................................................. 23
Figure 12 - Telephone Line Connections .........................................................................................................................24
Figure 13 - 3-Wire Adapter .............................................................................................................................................. 24
Figure 14 - Antenna Installation ....................................................................................................................................... 25
Figure 15 - MASTR III System Module Pot Alignment .................................................................................................. 27
Figure 16 - T/R Shelf Interface Board.............................................................................................................................. 32
Figure 17 - T/R Shelf Interface Board (Rev. A)............................................................................................................... 35
Figure 18 - T/R Shelf Interface Board ( Rev. C) .............................................................................................................. 38
PRODUCT SPECIFICATION FOR CE MARKED EQUIPMENT
The MASTR® III Base Station and Auxiliary Receiver conform to the following Product Specifications.
EUROPEAN STANDARDS:
Safety: EN60065 (220 VAC applications only)
EMC: prETS 300 279 (August 1995)
TTD: Not Applicable
SUPPLEMENTARY INFORMATION:
The MASTR III Base Station and Auxiliary Receiver may be used in both trunked and conventional applications. Neither the
MASTR III Base Station nor the Auxiliary Receiver may be connected to leased lines in Europe without an additional linebarrier protection device.
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LBI-38636S
MAXIMUM PERMISSIBLE EXPOSURE (MPE) LIMITS
Do not transmit with this basestation and antenna when persons are within the MPE Radius of the antenna. The MPE Radius
is the minimum distance from the antenna axis that ALL persons should maintain in order to avoid RF exposure higher than
the allowable MPE level set by the FCC.
FAILURE TO OBSERVE THESE LIMITS MAY ALLOW ALL PERSONS WITHIN
THE MPE RADIUS TO EXPERIENCE RF RADIATION ABSORPTION, WHICH
EXCEEDS THE FCC MAXIMUM PERMISSIBLE EXPOSURE (MPE) LIMIT. IT IS
THE RESPONSIBILITY OF THE BASESTATION OPERATOR TO ENSURE THAT
THE MAXIMUM PERMISSIBLE EXPOSURE LIMITS ARE OBSERVED AT ALL
WARNING
DETERMINING MPE RADIUS
THE MAXIMUM PERMISSIBLE EXPOSURE RADIUS HAS BEEN ESTIMATED TO BE A RADIUS OF 24 FEET
MAXIMUM ASSUMING THE HIGHEST EFFECTIVE RADIATED POWER (ERP) ALLOWABLE UNDER FCC
RULES FOR BASESTATION ANTENNA INSTALLATIONS. THIS ESTIMATE IS MADE ASSUMING
MAXIMUM ALLOWABLE ERP LEVEL BY THE FCC AND 100 PERCENT DUTY CYCLE. THE MPE
CALCULATIONS WERE MADE ASSUMING WORST CASE IN EACH BAND WITH RESPECT TO
FREQUENCY, ERP AND LIMIT. THE MAXIMUM ALLOWABLE ERP WAS DETERMINED FROM THE
APPLICABLE PART 90 RULES REGARDING POWER LIMITATION ( 90.205, 90.309, 90.635 ). THE LIMIT
USED WAS FOR UNCONTROLLED EXPOSURE. THE FORMULA USED WAS DERIVED FROM OET 65,
SECTION 2, EQUATION 4.
TIMES DURING BASESTATION TRANSMISSION. THE BASESTATION
OPERATOR IS TO ENSURE THAT NO BYSTANDERS COME WITHIN THE
RADIUS OF THE MAXIMUM PERMISSIBLE EXPOSURE LIMITS SHOWN BELOW.
SAFETY TRAINING INFORMATION
YOUR M/A-COM MASTR III BASESTATION GENERATES RF
ELECTROMAGNETIC ENERGY DURING TRANSMIT MODE. THIS BASESTATION
IS DESIGNED FOR AND CLASSIFIED AS “OCCUPATIONAL USE ONLY”
MEANING IT MUST BE USED ONLY IN THE COURSE OF EMPLOYMENT BY
INDIVIDUALS AWARE OF THE HAZARDS AND THE WAYS TO MINIMIZE SUCH
HAZARDS. THIS BASESTATION IS NOT INTENDED FOR USE BY THE “GENERAL
POPULATION” IN AN UNCONTROLLED ENVIRONMENT. IT IS THE
WARNING
This basestation has been examined and complies with the FCC RF exposure limits when persons are beyond the MPE radius
of the antenna. In addition, your M/A-COM basestation complies with the following Standards and Guidelines with regard to
RF energy and electromagnetic energy levels and evaluation of such levels for exposure to humans:
• FCC OET Bulletin 65 Edition 97-01 Supplement C, Evaluating Compliance with FCC Guidelines for Human
Exposure to Radio Frequency Electromagnetic Fields.
• American National Standards Institute (C95.1 – 1992), IEEE Standard for Safety Levels with Respect to Human
Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz.
RESPONSIBILITY OF THE BASESTATION OPERATOR TO ENSURE THAT THE
MAXIMUM PERMISSIBLE EXPOSURE LIMITS DETERMINED IN THE PREVIOUS
SECTION ARE OBSERVED AT ALL TIMES DURING TRANSMISSION. THE
BASESTATION OPERATOR IS TO ENSURE THAT NO BYSTANDERS COME
WITHIN THE RADIUS OF THE MAXIMUM PERMISSIBLE EXPOSURE LIMITS.
6
American National Standards Institute (C95.3 – 1992), IEEE Recommended Practice for the Measurement of
•
Potentially Hazardous Electromagnetic Fields – RF and Microwave.
TO ENSURE THAT YOUR EXPOSURE TO RF ELECTROMAGNETIC ENERGY IS
WITHIN THE FCC ALLOWABLE LIMITS FOR OCCUPATIONAL USE, ALWAYS
ADHERE TO THE FOLLOWING GUIDELINES:
LBI-38636S
CAUTION
DO NOT operate the basestation with an antenna that would cause an ERP in excess of that
allowable by the FCC.
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LBI-38636S
STATION SPECIFICATIONS
(GENERAL)
CABINET
Width 21.5 inches 23.1 inches
Depth 18.25 inches 21.0 inches
Weight (note 1) 150 lbs (68 kg)
Rack Units (RU) (note 2)
Cabinet capacity 17 RU 33 RU
Radio 8 RU 8 RU
Duty Cycle (EIA) Tx and Rx at 100%
(continuous)
Operating Temperature -30°C to +60°C
Humidity (EIA) 90% at 50°C
AC Input Power 5 Amps at 120 Vac (-20%) 60 Hz
DC Input Power 33 Amps at 13.8 Vdc (transmit, full power)
Service Speaker 1 watt at 8 ohms
Service Microphone Dynamic
Notes:
1. Typical station consists of:
a. One T/R Shelf with plug-in modules.
b. One Power Amplifier.
c. One power supply unit.
d. One cabinet with doors.
2. One rack unit equals 1.75 inches.
37-INCH 69-INCH
Height 37.0 inches 69.1 inches
or
3 Amps at 230 Vac (-15%) 50 Hz
25 Amps at 13.8 Vdc (transmit, half power)
1.6 Amps at 13.8 Vdc (receive only, standBy)
1.75 Amps at 13.8 Vdc (receive only, 1 watt at
service speaker)
INTERFACE
Line Interface
Line Interface 2-wire or 4-wire (programmable)
Line Cancellation (2-wire) 20 dB amplitude only (programmable)
Line Input (line to transmitter)
Line Terminating Impedance 600 ohms (2-wire or 4-wire)
Line Input Level (adjustable) -20 dBm to +11 dBm
Frequency Response 300 Hz to 3000 Hz
Line Input (receiver to line)
Line Terminating Impedance 600 ohms (2-wire or 4-wire)
Line Output Level (adjustable) zero output to +11 dBm (ref at 1 kHz)
Frequency Response 300 Hz to 3000 Hz, ±1 dB
Remote Control (Tone)
Control Tones (Hz) 1050, 1150, 1250, 1350, 1450, 1550, 1650, 1750,
1850, 1950, 2050, & 2175
Secur-it 2175 Hz
Function Programmable
Hold 2175 Hz
DC Remote Control
Control currents -2.5 mA, ±6.0 mA, ±11.0 mA
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LBI-38636S
PUBLICATIONS INDEX
MASTR III BASE STATION Systems Combination Package.............................................................. LBI-38775
T/R Shelf .........................................................................................................................................LBI-38637
System Module................................................................................................................................ LBI-38764
LBI-39176
Power Module .................................................................................................................................LBI-38752
MASTR III PC Programmer...................................................................................................................... TQ-3353
MASTR III Installation Manual ............................................................................................................. LBI-38636
RF Module Test Fixture ......................................................................................................................... LBI-38805
MASTR III Utility Handset.................................................................................................................... LBI-38599
RF Package: High Band (136 - 174 MHz) .............................................................................................LBI-38754
Transmit Synthesizer Module.......................................................................................................... LBI-38640
Receive Synthesizer Module ........................................................................................................... LBI-38641
Receiver Front End Module ............................................................................................................LBI-38642
IF Module........................................................................................................................................ LBI-38643
LBI-39123
Power Amplifier .............................................................................................................................. LBI-38531
Duplexer .......................................................................................................................................... LBI-38763
RF Package: UHF (380 - 512 MHz)....................................................................................................... LBI-38675
Transmit Synthesizer Module.......................................................................................................... LBI-38671
Receive Synthesizer Module ........................................................................................................... LBI-38672
Receiver Front End Module ............................................................................................................LBI-38673
LBI-39129
IF Module........................................................................................................................................ LBI-38643
LBI-39123
Power Amplifier .............................................................................................................................. LBI-38674
Duplexer .......................................................................................................................................... LBI-38763
RF Package: 800 MHz............................................................................................................................ LBI-39025
Transmit Synthesizer Module.......................................................................................................... LBI-39026
Receive Synthesizer Module ........................................................................................................... LBI-39027
Receive RF Module......................................................................................................................... LBI-39028
IF Module........................................................................................................................................ LBI-39029
Power Amplifier ................................................................................................................ (100 W)LBI-39030
AE/LZB 119 3521/1
Power Amplifier .................................................................................................................(110 W)LBI-39127
Power Supply .................................................................................................................................. LBI-38550
Power Supply (800 MHz)....................................................................................................................... LBI-38551
Emergency Power (Battery Charger)...................................................................................................... LBI-38625
Auxiliary Receiver VHF......................................................................................................................... LBI-39114
UHF................................................................................................................................................. LBI-39115
800................................................................................................................................................... LBI-39113
Voice Guard System Manual.................................................................................................................. LBI-31600
Voice Guard/Aegis ................................................................................................................................. LBI-38879
LBI-38880
LBI-38881
Adaptive Multipath Pop Filter (AMPF) .................................................................................. AE/LZT 123 3244/1
Antenna Systems .................................................................................................................................... LBI-38983
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LBI-38636S
NOTE: Indented maintenance manuals are included with the header (cover) maintenance manual.
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LBI-38636S
Figure 1 - Typical 37-inch MASTR III Stations
SAFETY SUMMARY
The following general safety precautions must be
observed during all phases of operation, service, and
repair of this product. Failure to comply with these
precautions or with specific warnings elsewhere in this
manual violates safety standards of design, manufacture,
and intended use of the product. M/A-COM assumes no
liability for the customer’s failure to comply with these
standards.
GROUND THE EQUIPMENT
To minimize shock hazard, the station equipment
cabinet must be connected to an electrical ground. The
equipment supplied is equipped with a three-conductor
AC power cord. The power cord must be plugged into an
approved three-contact electrical outlet with the
grounding wire firmly connected to an electrical ground
(safety ground) at the power outlet. The power cord meets
International Electrotechnical Commission (IEC) safety
standards.
REPLACEMENT OF PLUG-IN CIRCUIT
MODULES
Component or module replacement and internal
adjustments must be made by qualified maintenance
technicians.
Do Not replace components or
modules with power applied.
CAUTION
ELECTROSTATIC DISCHARGE SENSITIVE COMPONENTS
This station contains CMOS and other circuit
components, which may be damaged by electrostatic
discharge. Proper precaution must be taken when
handling circuit modules. As a minimum, grounded wrist
straps should be used at all times when handling circuit
modules.
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LBI-38636S
DO NOT SUBSTITUTE PARTS OR
MODIFY PRODUCT
Because of the danger of introducing additional
hazards, do not install substitute parts or perform any
unauthorized modifications to the product.
INTRODUCTION
This manual describes the installation and
connections for a typical MASTR III station combination.
Information provided includes suggested locations and
installation of equipment and hardware, interconnection
and assembly diagrams, alignment instructions, and
troubleshooting suggestions.
The MASTR III cabinet normally includes the
Transmitter/Receiver Shelf, the Transmitter Power
Amplifier, and a Station Power Supply. The assemblies
are mounted in a 37-inch cabinet. Optional 69- inch or
two stacked 37-inch cabinets are available.
CABINET
The system is contained in a 37-inch cabinet with
improved ventilation for greater reliability. The cabinet
can also house optional equipment such as a Duplexer,
Charger, Gell Cell batteries, or Auxiliary Receiver.
STATION POWER SUPPLY
The Station Power Supply provides all necessary
power to run the station. It provides 13.2 volts at 33 amps
to the station from an AC source. The source voltage
depends on the particular area and power sources
available. The power supply is normally mounted beneath
the T/R Shelf.
UNPACKING EQUIPMENT
Unpack the station and carefully inspect each item. If
any damage has occurred to the equipment during
shipment, immediately file a claim with the freight
carrier. AC power adequate to meet system requirements,
environmental control, and digital or voice grade phone
lines must be available at the site prior to installation.
SITE PREPARATION AND
INSTALLATION
CABINET INSTALLATION
The MASTR III station cabinet is designed for
servicing from the front. However, the system may also
be serviced from the rear when adequate space is
available. The cabinet should be mounted on a level, solid
surface.
If rear servicing is desired, cabinets should be setup
with a minimum of 24-inches of clearance in the rear and
between cabinets or wall to permit ventilation and room
for the service-man to move between and behind the
cabinets.
If space is at a premium or if servicing is to be made
from the front only, then cabinets should be setup with a
minimum of 18-inches of clearance in the rear and 12inches between cabinets to permit ventilation. However,
access to the rear of the cabinets may still be necessary in
order to install or repair antenna or power cables.
Single and double stacked 37-inch cabinets must be
securely anchored to the floor according to the footprint
shown in Figure 2 and following single or double stacked
installation instructions.
TRANSMITTER/RECEIVER SHELF
The MASTR III Transmitter/Receiver (T/R) Shelf
contains the station control electronics for dc/tone remote,
re-mote/repeater, or repeater only applications. The
station control electronics consists of a Backplane board,
Power Module, System Module, and an Interface Board.
The back-plane also connects the RF Section which
consists of the Receiver Synthesizer Module, First IF
Module, Second IF Module, and the Transmit Synthesizer
Module.
TRANSMITTER POWER AMPLIFIER
The Transmitter Power Amplifier is mounted directly
behind the T/R Shelf. Cabling from the output of Power
Amplifier will depend on the system configuration.
12
Single 37-inch Cabinet Installation
The station provides for front and rear door servicing
or front door only servicing in tight space situations. The
front and rear of the station must be kept clear of
obstructions so that the serviceman can easily remove the
front and rear doors for servicing. Also, the front and rear
air vent louvers and rear cable outlets must be free of
obstructions.
Figure 2 - 37 Inch Mounting Footprint
LBI-38636S
serviceman can easily remove the front and rear doors for
servicing. Also, the front and rear air louvers and rear
cable outlets must be free of obstructions. Leave a
minimum of 12-inches of space on each side of the
cabinets to avoid obstructing the louver air vents. With
the bottom cabinet in position, secure it to the floor as
shown in Figure 2 with 1/2-inch bolts and anchors.
Remove the four plastic plugs in the top surface of the
bottom cabinet (by squeezing the plastic retaining barbs
together from the inside of the cabinet and pushing the
plug up and out).
Position the top cabinet on the bottom cabinet. Align
the fixing holes and bolt the cabinets securely together
using 1/2 inch bolts, washers, and locknuts (supplied in
hardware kit 344A3450G7) as shown in Figure 4.
It will be necessary to remove the front and rear
covers and some internal components to allow access to
the top and bottom securing holes.
Figure 3 - 37-Inch Cabinet
Using the four holes are provided in the bottom
surface of the cabinet, the cabinet must be securely bolted
to the floor with 1/2" bolts and anchors as shown in
Figures 2 and 3. It will be necessary to remove the front
and rear door covers and some internal components to
allow access to the bottom securing holes.
Double Stacked 37-inch Cabinet installation
For limited floor space situations, two 37-inch
MASTR III cabinets may be stacked one upon the other.
This requires that the bottom cabinet be securely bolted to
the floor surface and the top cabinet securely bolted to the
top surface of the bottom cabinet, as shown in Figure 4.
Ensure first that the floor is strong enough to support
the weight of the two cabinet configuration and that
adequate ceiling height is available. Ensure the front and
rear, of the station cabinets are clear of obstructions so
Figure 4 - Stacked 37-Inch Cabinets
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LBI-38636S
ELECTRICAL CONNECTIONS
AC Power
The station will be received with the power cord
bundled and stored in the bottom of the cabinet. Remove
the twist tie from the AC power cord, unravel and feed the
cord through one of the rear cable holes. It may be helpful
to remove the grommet from the hole before passing the
cord through and reinstalling it afterwards.
A separate 15 to 20 Ampere, 120 Vac, 60 Hertz
electrical circuit should be provided for the station. A 120
volt grounded AC outlet for the station should be located
within six feet of the lower rear of the cabinet. The power
cord for the 120 Vac Power Supply comes with a
grounded 120 Vac molded plug attached. Check the
electrical code to ensure the power outlet complies with
local ordinances.
If a 240 Vac, 60 Hz source is used for the station, an
external step-down transformer (similar to 19C307148P1)
must be used.
For 230 Vac, 50 Hz applications, the station power
supply is equipped with a power cord, less connector, to
permit connection to an acceptable electric circuit. A plug
meeting local electrical codes must be supplied by the
customer. Make sure the station power supply is
connected to an outlet having the same configuration as
the plug. No adapters should be used in this configuration.
The equipment should be connected to a good earth
ground using a ground wire of adequate size. A ground
stud is provided for a separate cabinet ground. Use No. 14
or larger wire (depending on local ordinances and system
requirements) for connecting the cabinet to a good
building ground. After the ground lead from the power
cable is connected to the building ground, check for
continuity between building ground and the cabinet.
Microphone
The local microphone or utility handset may be
attached to the station through the MIC port on the front
of the T/R Shelf (Figure 6), the connections are shown in
Figure 5.
Antenna
The antenna cable may be routed through the top rear
or bottom rear of the cabinet directly to the appropriate
connector within the station, depending upon the
configuration.
TELEPHONE LINE CHARACTERISTICS
Telephone Lines
The type of telephone lines required for the
installation will depend on how the station is controlled
and if it is being used for simplex or duplex operation.
Generally, both 4-wire Audio and E & M Signaling
options are used to interface between the radio and carrier
systems. However, 2-wire Audio can be used in the twoway radio portion of the control system if hybrids are
installed to provide transition between the 2-wire and 4wire connections. Usually the E & M Signaling is
separated from the audio (separate line) in both 2-wire
and 4-wire installations.
Figure 5 - Microphone Connections
Types Of Voice Grade Lines
Telephone lines are normally obtained from a
communications common carrier ("telephone company"
for our purposes here). When a voice grade (as contrasted
to a "data line") telephone line is requested, there is no
way of knowing just what type of line will be received
from the phone company.
In addition, the telephone company may supply one
type of line first, and later change it to another type
without any notification to the user. One of the following
types of telephone line can be expected:
1. Wire lines with no amplifiers
2. Wire lines with amplifiers added to compensate
for line loss
3. Facilities derived from carrier (multiplex)
These lines have different operating characteristics,
and each must be treated differently. In large systems, all
three types of lines can be provided. In long haul
applications, a system can consist of two or three of these
types of lines in tandem (tied together end-to-end).
The first type is WIRE LINE WITH NO
AMPLIFIERS. These are the same lines that have been
used for years to control dc systems. These are the easiest
to work with since they include no problem-causing
electronic equipment. These lines are normally found in
14
LBI-38636S
less populated areas where the phone company has not yet
switched to carrier systems. These lines have a fixed
amount of loss, which varies with frequency, temperature,
from deterioration of splices, and from moisture getting
into the cables. When these cables get old, the phone
company sometimes applies DC current to improve the
joints and lower the line loss. In this case, the line is not
usable for DC control.
Normally, a +10 dBm test tone can be applied to
these lines. These lines do not normally include any type
of voice limiters.
The second type of line is a WIRE LINE WITH
AMPLIFIERS. These lines are normally supplied when
the loss of available lines is too high. An amplifier or
several amplifiers are added to the line to make up for the
loss.
One commonly used amplifier is the E-6 repeater.
This amplifier will pass DC current and they have been
used on DC lines for years. These amplifiers include
limiters, which start limiting at somewhere around 0 dBm
input to the amplifier. The limiters do not cause any real
problems on DC systems since only the voice peaks are
clipped. However, special care must be used when
applying them to tone remote control systems.
Each amplifier can be adjusted for up to 12 dB of
gain. If the loss is more than 12 dB, one or more
amplifiers may be added. The amplifier(s) can be placed
at any point in the line.
The third type of telephone line is a Derived Facility
using carrier equipment. Since this is the most
complicated, more care is required when connecting radio
equipment. This type of line will be available more often
in the future.
The telephone company supplies two wires at each
end of the circuit. Each two-wire end goes to some point
in the circuit where it is converted to a four-wire circuit
and then connected to the carrier equipment. A four-wire
circuit can be ordered if that is what is required. At the
other end, it is taken out of the carrier equipment and
converted back to the two-wire circuit. The carrier
equipment has a transmit path and a receive path. The
gain is adjustable each way.
Figure 6 - T/R Shelf Connections
15
LBI-38636S
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