Acnodes OPC 8190 - Manual (Page 21)

2.2 Serial Ports Interface
OPC8190 has four serial ports. COM1 is RS-232/422/485, while
COM2, COM3, and COM4 are RS-232.
The following table shows you the pin assignments of this connector:
Pin Signal Pin Signal
1 Data Carrier Detect (DCD) 6 Data Set Ready (DSR)
2 Receive Data (RXD) 7 Request To Send (RTS)
3 Transmit Data (TXD) 8 Clear To Send (CTS)
4 Data Terminal Ready (DTR) 9 Ring Indicator (RI)
5 Ground (GND)
In addition, COM1 can be set for RS-232/422/485 by jumper. The
jump setting is listed as below:
COM1 JP11 JP12 JP13
RS-232 (default) 3-5, 4-6 3-5, 4-6 1-2
RS-422 1-3, 2-4 1-3, 2-4 3-4, 7-8
RS-485 1-3, 2-4 1-3, 2-4 5-6, 7-8