Table 2-1 EIA RS-232-C Connector Signals
Pin Number Description Pin Number Description
1 Protective ground 14 (not used)
2 Transmitted data 15 Transmit clock
3 Received data 16 (not used)
4 Request to send 17 Receive clock
5 Clear to send 18 (not used)
6 Data set ready 19 Speed select
(secondary request to send)
7 Signal ground (common return)
8 Carrier detect 20 Data terminal ready
9 (not used) 21 (not used)
10 (not used) 22 Ring indicator
11 Same as pin 19 23 Same as pin 19
12 Speed indicator
(secondary carrier detect)
24 (not used)
25 (not used)
13 (not used)