Samyung AIS Transponder SI30, Connection to PC:
On the backside of the SI30 unit there is multi-connector marked "RS-422 Interface".
It uses pins 22, 23 for NMEA output, which have to be connected to pin5 and pin2 respectively of the serial port of the PC (9-pin RS-232 port).
SI30 pin 22 -> Pin 5 on PC
SI30 pin 23 -> Pin 2 on PC
Here is the connection diagram of Samyung SI30 AIS transponder: