RTS BP300 User Manual
User Manual
MODEL BP-300
Portable Belt Pack User S tation
9350-1786-00 Rev H 09/2006
PROPRIETARY NOTICE
SHIPPING TO THE MANUFACTURER
The product information and design disclosed herein were originated by
and are the property of Telex Communications, Inc. Telex reserves all
patent, proprietary design, manufacturing, reproduction, use and sales
rights thereto, and to any article disclosed therein, except to the extent
rights are expressly granted to others.
COPYRIGHT NOTICE
Copyright 2006 by Telex Communications, Inc. All rights reserved.
Reproduction, in whole or in part, without prior written permission from
Telex is prohibited.
WARRANTY NOTICE
See the enclosed warranty card for further details.
CUSTOMER SUPPORT
Te chnical questions should be directed to:
Customer Service Department
RTS/Telex Communications, Inc.
12000 Portland Avenue South
Burnsville, MN 55337 USA
Telephone: 800-392-3497
Fax: 800-323-0498
Factory Service: 800-553-5992
All shipments of product should be made via UPS Ground, prepaid (you
may request from Factory Service a different shipment method). Any
shipment upgrades will be paid by the customer. The equipment should
be shipped in the original packing carton. If the original carton is not
available, use any suitable container that is rigid and of adequate size. If
a substitute container is used, the equipment should be wrapped in paper
and surrounded with at least four (4) inches of excelsior or similar
shock-absorbing material. All shipments must be sent to the following
address and must include the Proof of Purchase for warranty repair.
Upon completion of any repair the equipment will be returned via
United Parcel Service or specified shipper, collect.
Factory Service Department
Telex Communications, Inc.
8601 East Cornhusker Hwy.
Lincoln, NE 68507 U.S.A.
Attn: Service
RETURN SHIPPING INSTRUCTIONS
Customer Service Department
Telex Communications, Inc. (Lincoln, NE)
Telephone: 402-467-5321
Fax: 402-467-3279
Factory Service: 800-553-5992
Please include a note in the box which supplies the company name,
address, phone number, a person to contact regarding the repair , the type
and quantity of equipment, a description of the problem and the serial
number(s).
TABLE OF CONTENTS
PROPRIETARYNOTICE
....................................................
.
.
2
COPYRIGHTNOTICE
PATENTNOTICE 2
UNPACKING
WARRANmIWORMATION 2
RETURN
SECTION
1.1DESCRIFTON
1.3 SPECIFICAlIONS 6
SECTION2.INSTALLATION
2.1
POWER
2.2 TYPE OF MOUNTING 7
2.3 CHOOSING HEADSETS
2.4CABLINGREQULREMENTS
2.4.1 WIRE SIZE AND
AND
SHlPPING INSTRUCTIONS 2
1:
DESCRIPTION AND SPECIFICATIONS
REQUlREMENTS. TYPE OF SYSTEM. POWERING METHOD
.....................................................
2
........................................................
INSPECTION 2
...............................................
.................................................
............................................
..................................
.......................................................
5
5
.....................................................
................................................
AND
POWER SUPPLY
(IES)
......
7
7
...................................................
..................................................
...............................................
MAXIMUM
OPERATING DISTANCE
............................
9
9
8
2.5MECHANICAL
2.6SYSTEMCHECK
2.7 STANDARD
SECTION3.OPERATION 13
3.1 OPERATING CONTROLS
3.2 OPERATION
SECTION
4.1
WHERE
4.2 MECHANICAL PARTS
4.3
ELECTRICAL
SECTION
4:
TO OBTAIN
5:
.......................................................
......................................................
USER
STATION CONNECTIONS
.....................................
10
10
10
..................................................
AND
CONNECTORS
........................................................
REPLACEMENT PARTS
PARTS
...................................................
PARTS
DIAGRAMS 1 DRAWINGS
...................................................
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13
13
15
15
15
15
19
MICROPHONE
Page
4
0
3
()
Ll'
SECTION
1.1
DESCRIPTION
The Model BP300 is a portable, two-channel inter-
com user station. The user station is designed to be
used in a full duplex, conference line intercom sys-
tem.
Conference Line Intercom Svstem (Figure 1-1)
A
of people to talk and listen on a single channel.
On this channel, all users can listen when one or
more other users are talking (conferencing). Up
to
conference bus).
Full duplex operation allows two way conversation
at the same time, that is, one user can interrupt a
second user while the second user is still talking.
The BP300, with a headset, interfaces a human user
to the intercom system. The user talks
using the headset (or a handset). The headset con-
nects to the BP300 via a four conductor cable and
connector (optionally five or six pin). The BP300
connects to the system using a three conductor
"microphone" type cable. The BP300 contains four
controls: the volume control, the latching micro-
phone switch, the momentary microphone switch,
and the channel select switch. On the Model
BP300L, the momentary microphone switch is re-
placed with the call light button.
Volume Control
The volume control on the
to compensate for: user hearing differences, ambi-
ent noise variation, variations in headset
sensitivity, and variations in voices. The volume
control in the BP300 reduces distortion by driving
the headphone amplifier only
Microphone Switch(es1
In normal system operation, one or more users talk
and the others listen.
station allows the talker's microphone to
and allows the listeners to keep their microphones
disabled. In this condition, speech intelligibility is en-
hanced since background noise from other micro-
phones is not present.
On the Model BP300, a latching switch or momentary
push button turns the microphone on.
1:
DESCRIPTION & SPECIFICATIONS
conference line intercom system allows a group
75
users
can
share the same conference line (or
and
listens
a
BP300 has
as
much as needed.
A
microphone switch on each
wide range
/
handset
be
enabled
The momentaty push button allows quick 'bursts of
communication, especially useful in a high noise envi-
ronment. The latched position allows "hands freen
operation, when the user needs to have two way
conversation while performing another activity.
The Channel Select Switch
A
channel selector switch allows a choice of two
(optionally three) channels.
the
"1"
position the station talks and listens on chan-
nel
1,
on the "2"position, channel 2, and so on. On
larger systems the "1" position may be any system
channel (1 through 12 for example). Similarly, for
position
quirements under these conditions.
Call Light Push Button (BP300L, only)
Pushing this button transmits a call signal to all other
units on the channel selected by the channel selector
switch.
light push button to flash. The flash rate is 2 to
times a second. The call signal itself is a 20 kilohertz
signal.
Options (-DL,
The BP300 and BP3OOL use the CC33 card
indicated below. Codes at the end of each aragraph
indicate the card used. Codes are: *CC33 car$ **CC4O
card, ***CC45 card. (CC33 schematic is SD1464;
CC40/CC45 schematic is SD1427).
-DL: Dual Listen on two channels. The volume control is
changed to
The channel select switch routes the
knob follows the channel selector. The inside knob is the
non-talk, listen only channel.
-E:
the balanced program is fed in instead. Pins 2
input connections.
two knobs provides separate level controls for interwm
program.
-3CII: Three CHannel operation. Line and loop-through
connectors are changed to 4-pin from 3-pin. A 3-position
channel select switch replaces the 2-position switch.
-USMB: UnSwitched Microphone output, Balanced.
Deletes line loop-through. Level: -7dBm to S3dBm. The
USMB
systems such
telephone, radiotelephone, or Stage Announce.
-LP:
power to low volta e to wer the user station,
connector
the interwm line.
"2".
See Section 2.1 for DC powering re-
A
call signal on this channel will cause the call
-E,
-3CH,
-USMB, -LP)
a
dual
concentric potentiometer with two knobs.
Program Input, balanced. Deletes line loop-through,
A
dual
provides a line level microphone signal to other
as
an Interrupted Feedback System
Local
Power source. A small module converts AC line
is
provib;d.
#e unit does not use power from
When the switch is on
except
as
talk
signal. The outside
and
concentric potentiometer with
3 are the
(IFB),
a
separate
and
5
Page
5
1.3 BP300 SPECIFICATIONS
Current Source
Input DC Voltage
18
TW Mode
LP Option
Battery
DC Current Drawn from
no current from
Quiescent
BP300 23 milliamperes 210%
BP3OOL 33 milliamperes 210%
Operating, 25 ohm headphones
BP300 37 milliamperes
BP3OOL 45 milliamperes 210%
Operating, 25 ohm headphones
BP300L 60 milliamperes
Impedance Across Line 10,000 ohms, minimum
Environmental
Temperature
Operating 0.C to 60°C
Storage
Humidity
TW
line)
to 35 volts DC
15 to 35 volts DC
12 to 35 volts DC (reduced
performance)
TW
Line (Note: LP Option draws
2
10%
+
Call Light
f
10%
-
40°C to 85°C
Transfer Ratio
Output
I-leadphone Amplifier
Voltage Gain 34 dB
Output Voltage 8 volts peak-to-peak into 25
Output Power 112 watt peak into 25 ohms
Frequency Response 150 hertz to 8 kilohertz
Headphone
Impedance Range
NOTE: DO NOT USE HEADPHONES
IMPEDANCES LESS THAN
Sidetone
Adjustment Range
Call-Light
Signaling Frequency 20,000 hertz
Flashing Rate
Auxiliarv Connections
Headset Connector
Dynamic Microphone XLR
Carbon Microphone 114" standard phone jack,
3.3 milliamperes
=
3.3 millislemens
A
5 milliamperes into 200 ohms
=
-c
1
volt peak, nominal
25 to 600 ohms (600 to 2000 with
reduced levels)
-
20 dB to full on
A
5 hertz
type
3 circuit
/
volt
25
OHMS.
f
100 hertz
2 hertz
4-pin female
-t
WITH
Cl
3 dB
&
Operating
Noise Contribution
One unit -75 dBu
Ten units: -67 dBu
Microphone Preamplifier
Input Impedance 470 ohmsldynamic mic
Source Impedance 200 ohms, nominal
Maximum Input Level 150 millivolts
Fre uency Response 100 hertz to 10 kilohertz k3 dB
q-54 dBu input)
Limiter Range 30 dB
Carbon Mic
Excitation Current 10 milliamperes, nominal
Storage
5%
to 95% non-condensing
Line Connections
Input XLR type 3-pin female
Loop/External XLR type 3-pin male
Mechanical
Dimensions
Weight 1.0 pounds, 0.45 kilograms
Finish Clear, anodized aluminum
SPECIFICATION NOTES:
=
0 dBu
0 dBm
(0 dBu, open circuit)
0.775 volts rms.
=
1
milliwatt = 0.775 volts rms. into 600 ohm load
Note:
All
products and specifications subject to
H
x
6.00
152.4
change without notice.
3.50 W x
H
x
88.9
1.75 D inches
W
x
44.5 D, millimeters
Pagc
6
lo
I
I
SECTION
Follow the directions: "To Install the BP300n, below.
2.1
Method And Power Supply(ies)
Power Requirements
To maintain a bridging 10,000 ohms impedance to the
intercom line, the
DC. To operate in local power or battery modes, the
BP300 requires from +15 to +35 volts DC, but is
operable at reduced performance from +12 to
volts. Below that voltage, a safety circuit disables the
microphone switch on the
Twe of System
The BP300 can be installed in a (1) three wire system,
(2) two wire system, or (3) special two wire system.
power in^
Power is carried to the unit from a system power
supply using three different methods:
(1)
2:
INSTALLATION
Power Requirements, Type
BP300 requires +18 to +35 volts
Method
In a three wire system ("Series 17n type), the
power is separate from the audio and supplied
by
a central power supply.
Of
System, Powering
CC33 board.
+
17.9
A
voltage, cable resistartce, and surges.
approacli is
capacity.
In (3) above, a local power supply provides 12 to
volts DC at 120 milliamperes peak for each station,
or, for remote single station operation, two 9-volt
batteries in series may
In (1) and (3) above, the two wires carrying the audio
requlre one system termination consisting of a
ohm resistor and a 100 microfarad capacitor in series.
This combination is connected across the two wires.
If the capacitor is polarized, its negative terminal is
connected to the system circuit common.
To Install the BP300:
1.
2. Determine the mounting of the BP300: Portable
3. Read "Choosing Headsets or Handsets".
4. Determine the cabling requirements.
to
operate ti= system at no more than
be
used.
Determine the type of system in which the BP300
is to be installed. Determine the powering
method and power supply(ies).
or Permanent.
more prudent
80%
of
24
200
a
(2) In
(3)
In (1) above, the power supply is a regulated supply,
24
can operate up to 50 BP300 and 30 BP300L user sta-
tions.
For case (2) above, assuming the currents shown, the
power supplies versus maximum number of stations
powered are:
Power Supply
Model
Model PSI5 1.OA 27 16
Model PS3l 1.5A 41 25
N&:
allow for other variations such as lemnperaturc, litw
two wire system ("TW-e), the power and
audio may share the same wire. The power is
supplied centrally by a special "TW" type power
supply-
In a special two wire system (Local Power), each
BP300 is locally powered and operates on switch
channel two. The BP300s are interconnected
using two wire cable. Power is supplied by a bat-
tery or a local power supply. The local power
supply should be isolated from earth ground.
volts DC to 32 volts DC, 1.5 amperes. This supply
BP300 (37mA) BP300L (60mA)
PS8
(j.43AI
Operaiwn of a system at maxitnutn load docs not
11
7
&
5. Create a system block diagram
(if not already available), then install the system.
6. Verify correct system operation by using the
checkout procedure in this chapter (02.6).
Update the system block diagram, equipment list
and any other documentation to reflect the
stal1ed"configuration. If the system block dia-
gram was originally created by
a copy of the
to RTS Systems. This diagram will be used to up-
date the original documentation, and for future
service support.
2.2
Type Of Mounting
(1) One type of mounting for the BP300 is portable,
when it is worn on clothing or an equipment belt.
(2) Another type of mounting for the BP300 is
permanent or semi-permanent, either
mountn (sitting on a desk) or fastened to fur-
niture. Avoid placing the BP300 on a metal or
grounded metal surface. Contact between the
Model BP300 and metal surfaces may cause
unwanted noises on the intercom line.
"as
installedn system block diagram
equipment list
RTS
Systems, send
a
"as
"desk
in-
Page 7
23
Choosing IIeadscts
Introduction Headset or handset choice depends on
operating environment, operating requirements, and
personal taste.
Operating Environment Table 2-1 shows typical oper-
ating environments and the amount of background
noise present.
A very quiet operating environment, such as a
television studio, may require that sound does not
leak from the headphones, meaning the headphones
should have good "acoustic isolation".
A
very noisy or loud environment usually requires
headphones that prevent outside sound from leaking
in (again, good acoustic isolation), headphones that
can produce a loud, clear sound, and noise cancelling
as
microphones,
Understanding speech in a noisy environment re-
quires that the sound from the headphones is as loud
or louder than the sound leaking into the headphones
from the noisy environment.
well.
is 23 milliamperes for the BP300,33 milliamperes for
the BP300L).
Headphone Sound Isolation
The ability of headphones to shut out unwanted envi-
ronmental noise varies from none (0 dB isolation) to
about 118th as loud (30 dB isolation). The degree of
isolation depends both on the design of the headset
and the frequency content of the environmental
noise. Lightweight, "open" headsets such as the RTS
Systems
muff), have almost no (0 dB) isolation. The trade-off
is that the LH267LH268 are very comfortable and
can be worn for long periods (8 to 12 hours) without
physical discomfort from the earmuffs or headband.
The LH267LH268 are low impedance and can be
turned up loud.
Because there is less acoustic isolation, care must be
taken that the sound signals from the LH267LH268
are not unintentionally leaked into microphones.
The DT108PT109 headsets have an isolation rang-
ing from 10 dB to 20 dB.
LH267 (single muff) and LH268 (double
Loudness In general, the loudness of a headphone
depends upon its ability to absorb power at a given
voltage (impedance) and the efficiency of its design.
Practically, the impedance has a larger effect with
present day headsets.
Impedance Low impedance headphones are louder,
causing the
power supply. High impedance headphones are not
as loud, drawing less current from the power supply.
The BP300 design range of impedances for the head-
phone
Headphone impedances 600 to 2000 ohms will oper-
ate at reduced levels. In a double muff headset such
as the Beyer
50 ohm headphones connected in parallel resulting in
an impedance of 25 ohms.
Efficiencv The BP300 produces the loudest sound in
low impedance headphones such as the DT109. In
this headphone, one milliwatt of electrical power
produces
Practical Loudness The BP300
duce an SPL of
DT108 headset. Low impedance headsets such
DT108 and DT109 headsets, cause the BP300
BP300L to require more power from the power sup-
ply. With DT109 headsets, BP300 peak current is 75
milliamperes. BP300L peak current is
80 milliamperes. With 600 ohm headphones, peak
current is 30 milliamperes for the BP300,
40 milliamperes for the BP300L. (Quiescent current
BP300 to draw more current from the
part
of the headset is 25 ohms to 600 ohms.
DT109 sold by RTS Systems, there are
94
dB SPL (Sound Pressure Level).
/
BP300L can pro-
111
dB in each ear of a DT109 or
as
the
At least four companies, Telex, Setcom, David Clark,
and Carter Engineering sell headsets intended for
heavy industrial, aerospace, and military markets.
These headsets can provide acoustic isolation figures
of 20dB to 40dB. Generally speaking, these headsets
are heavier and less comfortable to wear.
Isolation, Headset
In high noise environments, the headset microphone
should be a noise cancelling type.
Comfort In general, the comfort of headsets depends
upon their weight, padding and design.
In the headset connecting cable, prevent coupling be-
tween the microphone and headphone leads
at least a shielded wire for the microphone, and a
separate pair of wires for the headphone(s). Better
isolation may be possible with a twisted, shielded pair
for the microphone leads. Do not allow headphone
ground to contact microphone ground or shield. Tie
the shield to microphone ground or microphone low.
Do not tie the shield to the case of the connector or
the case of the user station. In general the maximum
length for the headset cable is ten feet (3.1 meters).
Lengths over ten feet require a special extension
/
cable. Check with RTS Systems for help with longer
cables.
Microvhones
by
using
Page 8
2.4.
Cabling Requirements
2.4.1
Wire Size and Maximum Operating Distance
Wire sue determines the maximum operating dis-
tance (where the DC voltage drop is the limiting fac-
tor). The following equations apply for a conductor
sue of #22 AWG, a minimum user station voltage of
18.0 volts, and a minimum power supply voltage as
stated below.
For Models PS10, PS30, PS31, PS50, PS60 (Vmin
=
28.4 WC):
=
Distance,, (feet)
Distan%, (meters)
322,181
=
/
99,133
Itot
(milliamperes).
/Itot
(milliamperes)
Another benefit of not "earthn grounding the circuit
return is that it prevents the introduction'of'noise
through "earth" currents from other equipment. If
RTS
the
currents, it is likely that they will be heard
Systmes circuit ground conducts these
as
interfering noise on the communication line.
2.43
Signal
The number of conductors required to interconnect
user stations is:
-
No. of
No. of
Conductors Channels
=
For Models PS8, PSI5 (Vmin
Distanc&, (feet)
Distan%, (meter)
Example:
The BP300L with 25 ohm headphones uses
=
185,874
=
56,654
24.0 VDC):
/Itot
(milliamperes)
/
Itot
(milliamperes)
up to 60 milliamperes. With a PS8 supply the maxi-
mum operating distance for this station is 185,874160
=
milliamperes
3098 feet (944 meters). And with a
PS31 power supply the maximum operating distance
=
is 322,181160 milliamperes
5370 feet (1652 meters).
The maximum operating distance using a PS8 power
supply and a BP300 with 25 ohm phones (37
185,874137
*
h
>.'
2.4.2
=
5024 feet (1531 meters).
Grounding
mA)
is
System circuit ground should not be directly con-
nected to "earth" or "chassisn ground (directly means a
connection an ohmmeter would show). Each user
station is bypassed to its own chassis via a 0.1 mi-
crofarad capacitor, establishing a radio frequency
(RF) ground to reduce radio frequency interference
from radio transmitters.
To prevent a buildup of voltage across the system
ca-
pacitance, the power supply has a bleeder resistor to
chassis ground (22 kilohms). If the system has
no
RTS Systems power supply, add a bleeder resistor at a
central point in the system.
The benefit of not "earthn grounding the RTS System
circuit return is that continued
o~eration is ~ossible
during an accidental system grouid fault. This acci-
dental grounding can happen when
a
wire is pinched
or a cable scraped across a sharp edge. One acciden-
tal ground can
can
fault
be
tolerated by the system until the
be cleared and (with luck) before a second
ground fault can cause noise or overload or bring the
system down.
Wirin~ICabling (See Cable Wiring Diagrams in Sec-
tion
7,
Application Information)
"TW"
Two channel
applications, or single channel,
three wire applications may use either standard mi-
crophone cabfe (for conveGence) or two-twisted-pair
cable (less expensive than microphone cable). Stan-
dard
wire sue for the system is #22 gauge wire for
interconnection. For permanent installations each
channel should have
an
individually shielded twisted
pair of at least #22 gauge wire; such as Belden 8723
for 2 channels, and 8777 for 3 channels. For plenum
and
/
or 200" C wiring, use Belden 88723 and 88777.
The plenum cable has a slightly smaller diameter, is
Teflon insulated, and about three times the price of
Wire using Cable Wiring Diagrams, Section 7, to re-
duce interference and help maintain a low crosstalk
figure between channels.
The audio signal line level is between 10
dBu and
0 dBu (between 0.24 and 0.77 volts rms). These levels
are low enough to prevent crosstalk into other equip-
TV
ment (such as
mize external interference to the
cameras) yet high enough to mini-
TW
System.
The 200 ohm line impedance is high enough to allow
communication over line lengths of 1.6 kilometers
(one mile) and low enough to permit an adequate
speech bandwidth with 3.2 kilometers of accumulated
cable. In most systems the 200 ohm impedance gives
a high fidelity bandwidth with low losses.
When using equipment in rain or conditions of exces-
sive moisture, always protect the equipment with plas-
tic covers and make sure all cable connectors are
lifted out of mud, snow or moisture and protected
with plastic. Water mud and snow in connectors can
cause noise.
Page 9
2.4.4
Channel to Channel Crosstalk Control
2.7
Standard User Station Connections
In the
TW
Intercom System all channels share a com-
mon circuit ground return. Crosstalk due to common
ground resistance
be reduced by using
22
gage
can
shielded cable, and paralleling shield drain wires with
circuit return wires. Capacitive crosstalk can be re-
duced by using two shielded pair. One wire of one
pair connects to channel one (pin
other pair connects to channel two (pin
2),
one wire of the
3),
the re-
maining wires are circuit return (pin 1). (See Cable
Wiring Diagram at back of manual).
Crosstalk reduction may also be achieved in some
CCD
cases using Model
214 Crosstalk Cancellation
Device.
25
Mechanical
The BP300 user station is either clipped to a user's
clothing for portable operation, or mounted on a
structure, camera or vehicle.
For permanent installation, temporarily remove the
electronics from the case. Drill, deburr and fasten the
case
as
necessary, then reinstall the electronics.
An
outline drawing for headset user station BP300 is
included at the end of the manual. This drawing pro-
vides mechanical information useful for permanent
and other type installations. This information in-
cludes overall dimensions, mounting information,
console cutout dimensions and weights.
It is recommended that space
access, cabling and servicing, such
loops, reaching
XLR
be.provided .for control
as
cabling
type
connector locks, local
service
power option power supplies and headset connectors
and cables.
If the headset connector is remoted, do not run this
cable close to interfering sources such
as
videom
monitors, power supplies and equipment with inter-
nal power supplies.
2.6
System Check
Dynamic Microphone headset connectors:
XLR-4-31 receptacle
Input level: -55 dBu, nominal
Output level to headphone:
1
-
Microphone low
Pin
2 - Microphone high
Pin
Pin
3
-
Headphone low
Pin 4
-
Headphone high
XLR-5-31 receptacle
Pin
1
-
Microphone low
Pin
2
-
Microphone high
-
Headphone low
Pin 3
Pin
4
-
Headphone high, left
-
Headphone high, right
Pin 5
XLR-6-31 receptacle
1
-
Microphone low
Pin
Pin
2 - Microphone high
-
Headphone low
Pin 3
-
Headphone high, left
Pin 4
Pin 5
-
Headphone high, right
Pin
6
-
Microphone switch
Carbon Microphone Headset Connector: 114 inch phone
jack (52):
Carbon Microphone: Tip (-15
Headphone: Ring (10
Common: Sleeve
LINE input and LOOPIEXTension connectors: (J3lJ4)
XLR-3-31 receptacle (for single-channel)
1
-
Common (low side of line)
Pin
Pin
2
-
Power
-
Channel
Pin 3
10 volts peak-to-peak,
open circuit.
dBV
input, nominal)
V
peak to peak open circuit)
Using three beltpacks with three headsets and three
persons, verify that all persons
can
intercommunicate
throughout the system. Verify that with all micro-
phone switches off and volume controls midway, only
a barely audible hiss is heard. The other two persons
should sound equally loud and clear to the third per-
son.
Page 10
XLR-3-31 receptacle (for two-channel line)
1
-
Common (low side of line)
Pin
Pin 2
-
Channel
Pin 3 - Channel
XLR-Q-31 receptacle (for three-channel line)
Pin
1
-Channel
Pin
2
-
Channel
Pin 3 - Channel 3
4
-
Common
Pin
1
(+DC)
2
1
2
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