25 PIN D-SUB MALE at the DTE (Computer).
25 PIN D-SUB FEMALE at the DCE (Modem).
| Pin | Name | Direction | Description |
|---|
| 1 | GND | --- | Shield Ground (n/a) (V.24 101) |
| 2 | TXD | Output | Transmit Data (BA) (V.24 103) |
| 3 | RXD | Input | Receive Data (BB) (V.24 104) |
| 4 | RTS | Output | Request to Send (CA) (V.24 105) |
| 5 | CTS | Input | Clear to Send (CB) (V.24 106) |
| 6 | DSR | Input | Data Set Ready (CC) (V.24 107) |
| 7 | GND | --- | System Ground (AB) (V.24 102) |
| 8 | CD | Input | Carrier Detect (CF) (V.24 109) |
| 9 | - | --- | RESERVED |
| 10 | - | --- | RESERVED |
| 11 | STF | Output | Select Transmit Channel (V.24 126) |
| 12 | S.CD | Input | Secondary Carrier Detect (SCF) (V.24 122) |
| 13 | S.CTS | Input | Secondary Clear to Send (SCB) (V.24 121) |
| 14 | S.TXD | Output | Secondary Transmit Data (SBA) (V.24 118) |
| 15 | TCK | Input | Transmission Signal Element Timing (DB) (V.24 114) |
| 16 | S.RXD | Input | Secondary Receive Data (SBB) (V.24 119) |
| 17 | RCK | Input | Receiver Signal Element Timing (DD) (V.24 115) |
| 18 | LL | Output | Local Loop Control (LL) (V.24 141) |
| 19 | S.RTS | Output | Secondary Request to Send (SCA) (V.24 120) |
| 20 | DTR | Output | Data Terminal Ready (CD) (V.24 108.2) |
| 21 | RL | Output | Remote Loop Control (RL) (V.24 140) |
| 22 | RI | Input | Ring Indicator (CE) (V.24 125) |
| 23 | DSR | Output | Data Signal Rate Selector (CH) (V.24 111) |
| 24 | XCK | Output | Transmit Signal Element Timing (DA) (V.24 113) |
| 25 | TI | Input | Test Indicator (TM) (V.24 142) |
