Asus B75M-PLUS - Manual (Page 28)

1-20 Chapter 1: Product introduction
The COM module is purchased separately.
10. Serial port connector (10-1 pin COM)
This connector is for a serial (COM) port. Connect the serial port module cable to this
connector, then install the module to a slot opening at the back of the system chassis.
B75M-PLUS
B75M-PLUS Serial port (COM) connector
COM
PIN 1
RXD DTR DSR CTS
DCD TXD GND RTS
RI
The S/PDIF module is purchased separately.
11. Digital audio connector (4-1 pin SPDIF_OUT)
This connector is for an additional Sony/Philips Digital Interface (S/PDIF) port. Connect
the S/PDIF Out module cable to this connector, then install the module to a slot
opening at the back of the system chassis.
SPDIF_OUT
+5V SPDIFOUT GND
B75M-PLUS
B75M-PLUS Digital audio connector