| 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 | ||||
| 10 | ||||
| 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 | ← | Receiver 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 |