# RS232

(At the DTE)
(At the DCE)

25 PIN D-SUB MALE at the DTE (Computer).
25 PIN D-SUB FEMALE at the DCE (Modem).

Pin | Name | ITU-T | Dir | Description
--- | --- | --- | --- | ---
1 | GND | 101 | - | Shield Ground
2 | TXD | 103 |  | Transmit Data
3 | RXD | 104 |  | Receive Data
4 | RTS | 105 |  | Request to Send
5 | CTS | 106 |  | Clear to Send
6 | DSR | 107 |  | Data Set Ready
7 | GND | 102 | - | System Ground
8 | CD | 109 |  | Carrier Detect
9 | - |  | - | RESERVED
10 | - |  | - | RESERVED
11 | STF | 126 |  | Select Transmit Channel
12 | S.CD | ? |  | Secondary Carrier Detect
13 | S.CTS | ? |  | Secondary Clear to Send
14 | S.TXD | ? |  | Secondary Transmit Data
15 | TCK | 114 |  | Transmission Signal Element Timing
16 | S.RXD | ? |  | Secondary Receive Data
17 | RCK | 115 |  | Reciever Signal Element Timing
18 | LL | 141 |  | Local Loop Control
19 | S.RTS | ? |  | Secondary Request to Send
20 | DTR | 108 |  | Data Terminal Ready
21 | RL | 140 |  | Remote Loop Control
22 | RI | 125 |  | Ring Indicator
23 | DSR | 111 |  | Data Signal Rate Selector
24 | XCK | 113 |  | Transmit Signal Element Timing
25 | TI | 142 |  | Test Indicator