User's Manual Part 5
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The following table describes S21 pin-outs, and relevant interface signals on S13 and S14
(T2000 logic PCB). S21 is the 9 way D-type connector mounted on the heatsink at the
rear of the radio.
The following diagram shows the pin designations of S21, viewed from the rear of the
radio.
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Pin No. Signal Description Level
S21-1 GND
S21-2 MIC Input for directional mic. audio
S21-3 GND
S21-4 GND
S21-5 GND
S21-6 FT-SWTCH Requests handsfree transmit.
S21-7 VOX Output signalling valid VOX opera-
tion.
S21-8 GND
S21-9 GND
S13-6 TX-LINE-IN Electret microphone audio switched
in during handsfree transmit.
300mVp-p at 60% mod. 1kHz
S13-7 RX-GTD-AF Used to provide VOX trunking
inhibit for received speech.
110mVrms at 60% mod. 1kHz
S13-11 OPTIONS-GND Provides the ground for the options
circuitry.
S14-1 +13.8V Powers the +8V regulator used to
supply audio circuitry
10.8V to 16V DC
available current 200mA
S14-2 +5V Used to supply power for the logic
circuitry.
available current 150mA
S14-3 BUSY Used to mute invalid audio when
transmitter has been inhibited.
carrier detect 0V = busy
S14-5 /PTT-TO-OPT Echoed to S14-6 for normal PTT
request. Switches off S13-6.
5V pull-up 0V = Tx
S14-6 /PTT-FRM-OPT Provides the signal for the radio to
transmit.
5V CMOS 0V = Tx
S14-7 /IN-LOCK Used to inhibit VOX Tx requests
when the radio is out of lock.
synthesiser lock detect 0V =
lock (lock-up time <20ms)
S14-11 CALL-SW Used by trunking software to mute
invalid audio.
5V CMOS 5V = mute