| Pin | Name | Direction | Color | Description |
| 1 | GND | ------ | | AA: Protective Ground |
| 2 | TXD | OUT | | BA: Transmit Data |
| 3 | RXD | IN | | BB: Receive Data |
| 4 | RTS | OUT | | CA: Request to Send |
| 5 | CTS | IN | | CB: Clear to Send |
| 6 | DSR | IN | | CC: Data Set Ready |
| 7 | GND | ------ | | AB: Signal Ground |
| 8 | CD | IN | | CF: Carrier Detect |
| 9 | - | - | | RESERVED - Positive test |
| 10 | - | - | | RESERVED - Negative test |
| 11 | STF | OUT | | Select Transmit Channel |
| 12 | S.CD | IN | | SCF: Secondary Carrier Detect |
| 13 | S.CTS | IN | | SCB: Secondary Clear to Send |
| 14 | S.TXD | OUT | | SBA: Secondary Transmit Data |
| 15 | TCK | IN | | DB: Transmission Signal Element Timing |
| 16 | S.RXD | IN | | SBB: Secondary Receive Data |
| 17 | RCK | IN | | DD: Receiver Signal Element Timing |
| 18 | LL | OUT | | Local Loop Control |
| 19 | S.RTS | OUT | | SCA: Secondary Request to Send |
| 20 | DTR | OUT | | CD: Data Terminal Ready |
| 21 | RL | OUT | | Remote Loop Control |
| 22 | RI | IN | | CE: Ring Indicator |
| 23 | DSR | OUT | | CH/CI: Data Signal Rate Selector |
| 24 | XCK | OUT | | DA: Transmit Signal Element Timing |
| 25 | TI | IN | | Test Indicator |