Industrial Data Systems IDS 160 - Manual (Page 39)

------------- RS232 INPUT CONNECTIONS -------------
signal name direction pin number
RXD INPUT to IDS 160 3
RTS OUTPUT from IDS 160 4
GND 7
-------------- CURRENT LOOP INTERFACE --------------
INPUT Clt + 8
Clt - 22
Note: Pulse input uses pins 15(+) and 22(return). The pulse
signal voltage should be 24V. Consult the factory for
other voltage ranges.