GE MDS SD Series Technical Manual page 34

Table 9. COM2 Pin Descriptions — Radio in RS-485 Mode
Pin Radio Input/
Number Output
6 OUT
7 IN
8 OUT
9 --
COM2 PORT NOTES:
RXD+ / RXB and RXD– / RXA are data sent to the radio to be transmitted
RXD+ / RXB is positive with respect to RXD– / RXA when the line input is a "0"
TXD+ / TXB and TXD– / TXA are data received by the radio and transmitted
TXD+ / TXB is positive with respect to the TXD– / TXA when the line output is a "0"
24
board.
Alarm Output — Behavior is user-configurable. Default behavior: A high on
this pin indicates an alarm condition; a low indicates normal operation.
RXD+/RXB (Received Data +) — Non-inverting receiver input
TXD+/TXB (Transmitted Data +) — Non-inverting driver output.
Reserved — User I/O for special applications
Figure 22. RS-485 Wiring Arrangements
SD Series Technical Manual
Pin Description
MDS 05-4846A01, Rev. I