What are the connections on the OPTO-4?
The RS232 end is a female 9-pin D-Sub DB9 connector following the standard 9-pin RS232 pin out specification.
The other end has bare wires. An isolated input pair A/+ and B/- for connection to an NMEA Talker, using RS422 voltage levels. A non-isolated output pair A/+ and ground for connection to an isolated listener, using RS232 voltage levels. There is also a shield wire at this end which connects through to the DB9 shield.