Pin Number

Direction of signal:

1

Protective Ground

2

Transmitted Data (TD) Outgoing Data (from a DTE to a DCE)

3

Received Data (RD) Incoming Data (from a DCE to a DTE)

4

Request To Send (RTS) Outgoing flow control signal controlled by DTE

5

Clear To Send (CTS) Incoming flow control signal controlled by DCE

6

Data Set Ready (DSR) Incoming handshaking signal controlled by DCE

7

Signal Ground Common reference voltage

8

Carrier Detect (CD) Incoming signal from a modem

20

Data Terminal Ready (DTR) Outgoing handshaking signal controlled by DTE

22

Ring Indicator (RI) Incoming signal from a modem