Accessories Connectors
The functions of the 25-pin accessories connectors, ACC-J1 to ACC-J4, are listed in Table 1. The
connectors include PTT and CW control lines, audio and baseband lines for external equipment,
auxiliary power output, serial RS-232 asynchronous data interfaces, and additional dedicated
handshaking and control lines. The functions supported by the serial data interfaces are determined
by the RM125/RM125R software.
Table 1. 25-Pin Accessories Connector, Pin Functions
Pin Designation
Description
1 SPKR-
Differential output to the external 8
Ω
, 8W speaker
2 EXT RX DATA-
Baseband output (0 dBm, 600
Ω
)
3 SPKR+
Differential output to the external 8
Ω
, 8W speaker
4 EXT RX AUDIO+
5 EXT RX AUDIO-
Differential received audio output (0 dBm, 600
Ω
; not controlled by volume, but
affected by squelch)
6 EXT TX AUDIO+
7 EXT TX AUDIO-
Differential transmit audio input (600
Ω
input impedance; 0 dBm is required for
full power)
8 PTT IN VOICE
Transmission command (short to ground) for voice signals
9 PTT IN DATA
Transmission command (short to ground) for data signals
10 PTT IN CW
Transmission command (short to ground) for CW (Morse) signals
11 SW A+
Primary DC voltage current limited output (max 1A)
12 DSI/KW C C
BDM
–
Data serial in/kW amplifier channel change
13 KW ON/OFF
kW amplifier power on/off output
14 EXT RX DATA+
Baseband output (0 dBm, 600
Ω
)
15 RXA
Receive input (point-to-point protocol to host/HLC)
16 TXA
Transmit output (point-to-point protocol to host/HLC)
17 EX RESET
External RESET input (for BDM)
18 GND
Ground
19 KW PTT
PTT output to kW amplifier
20 EXT ALARM
External alarm output (open collector, pulled to ground when external alarm is
activated
21 VPP
Flash programming voltage, input to BDM
22 DSC/KW_ALC
BDM – Data serial clock/kW amplifier ALC
23 SQ GATE
Squelch open/closed indication output
24 DSO/FAN ON/OFF BDM – Data serial out/Fan control
25 FREEZE/KW TU
BDM – Freeze/kW amplifier tune
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