| Pin | Type | Description / Signal type | Connection /
Measuring notes |
|---|
| 1 | E | Terminal 30 voltage supply | Fuse F57 |
| | | |
| 2 | | Not used | |
| | | |
| 3 | | Not used | |
| | | |
| 4 | | Not used | |
| | | |
| 5 | | Not used | |
| | | |
| 6 | | Not used | |
| | | |
| 7 | | Not used | |
| | | |
| 8 | M | Ground signal | Microphone |
| | | |
| 9 | E | Positive signal | Microphone |
| | | |
| 10 | M | Ground signal | Basic interface, telephone |
| | | |
| 11 | E | Positive signal | Basic interface, telephone |
| | | |
| 12 | M | Positive signal | Telephone connector |
| | | |
| 13 | A | Ground signal | Telephone connector |
| | | |
| 14 | M | Terminal 31 | Ground splice |
| | | |
| 15 | | Not used | |
| | | |
| 16 | | Not used | |
| | | |
| 17 | | Not used | |
| | | |
| 18 | E | Telephone ON signal | Telephone connector |
| | | |
| 19 | | Not used | |
| | | |
| 20 | | Not used | |
| | | |
| 21 | E/A | I-bus signal line | I-bus splice |
| | | |
| 22 | E | Telephone mute signal | Connector, telephone mute |
| | | |
| 23 | A | Telephone ON signal | Basic interface, telephone |
| | | |
| 24 | E | Voltage supply terminal R | Unloader relay, terminal R |
| | | |
| 25 | M | Low frequency negative signal | Basic interface, telephone |
| | | |
| 26 | A | Low frequency voltage signal | Basic interface, telephone |
| | | |