TN600 AC-3E Audio Control Card
MT-3/4 Radio Systems
TECHNICAL NOTES
Page 1 of 2
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TN600, REV 6-0-0, © May 2014
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The AC-3E audio control card is a plug-in module which provides audio routing, PTT routing, and muting control for
MT-3 and MT-4 radio systems. The audio control card includes the following features:
• jumper selectable audio routing, PTT, and muting.
• two independently adjustable hang timers adjustable from 50 milliseconds to 10 seconds.
• sockets for optional CTCSS decoders and encoders.
• low power analog and CMOS control circuitry.
• maximum standby current of 30 mA.
• true balanced 600 inputs and outputs for external equipment connection.
• optically isolated inputs and outputs for control by external equipment.
• suitable for Type 2 E&M signalling.
The AC-3E audio control card is fully confi gurable and can be used for all repeater and base station applications.
The audio control card module circuitry consists of three main functional blocks:
(1) The repeater control circuit, which allows all COR / PTT routing combinations for all repeaters.
(2) Optional CTCSS modules that can be installed at the factory or in the fi eld.
(3) Audio routing circuitry for active level control and distribution of receiver to transmitter audio
signals. The AC-3E is designed for applications where interface to external equipment is required.
All audio and control inputs/outputs are isolated by transformers and opto-isolators on the AC-3E.
External Audio Input: 600 , -25 dBm to 0 dBm adjustable
External Audio Output: 600 , -20 dBm to +3 dBm adjustable
Internal Audio Input: 4.7 K, -25 dBm to +3 dBm adjustable
The AC-3E audio control card includes four potentiometers on the front panel for adjusting internal audio levels.
Optional frequency select rotary switches can also be mounted on the front panel of the audio control cards, giving
easy access to 16 pre-programmed receiver and transmitter operating frequencies. Two switches are mounted on
the front of the audio control cards that can be confi gured to control CTCSS on / off or repeat disable. Confi guration
of all switches on the audio control card is set up at the factory at the time of order.
SQ . DI SA B L E
N
O
RMO
FF
RF NI
REFERENCE
INPUT
RECEIVER
FREQUENCY (MHz)
MADE IN CANADA
MODEL # CODE
TX
REFERENCE
INPUT
OFF
KEY TX
MIC
RF OUT
FREQUENCY (MHz)
NORM
TRANSMITTER
FREQUENCY (MHz)
MADE IN CANADA
MODEL # CODE
TRANSMITTER
CNTL
BUS
MIC RF OUT
AD
ANALOG
DIGITAL
NORM
OFF
KEY TX
MICMODE
REF
IN
USB
FREQUENCY (MHz)
MADE IN CANADA
MODEL # CODE
RECEIVER
NORM
SQ. DISABLE
OFF
CNTL
BUS
AD
RF NI
REF
IN
USB
FREQUENCY (MHz)
MADE IN CANADA
MODEL # CODE
57
57
AUDIO
CONTROL
RX A
RX B
TX A
TX B
TX A
TX B
5
9
13
5
9
13
PULL DOWN
TO REMOVE
VOL
SYSTEM REGULATOR
METER
+
-
MADE IN CANADA
ON
OFF
SPKR
INT
EXT
EXT
SPKR
OFF
POWER
ON
2
1
5
4
3
67
8
11
10
9
FUNCTION
12
57
57
AUDIO
CONTROL
RX A
RX B
TX A
TX B
TX A
TX B
5
9
13
5
9
13
PULL DOWN
TO REMOVE
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