| Pin | Signal | Description |
|---|
| 1 | GND | Digital ground |
| 2 | MIC/JCONN | External audio input from accessories or handsfree microphone. Multiplexed with junction box connection control signal |
| 3 | AGND | Analogue ground for accessories |
| 4 | TDA | Transmitted DBUS data to the accessories |
| 5 | M2BUS | Serial Bidirectional data and control between the handportable and accessories |
| 6 | HOOK/RXD2 | Hook indication. HP has a 100KE pull-up resistor |
| 7 | PHFS/TXD2 | Handsfree device power on/off, data to flash programming device |
| 8 | VCHAR | Battery charging voltage |
| 9 | GND | Digital ground |
| 10 | EAR/HFPWR | External Audio output to accessories or handsfree speaker |
| 11 | DSYNC | DBUS data bit sync clock |
| 12 | RDA | DBUS recieved data from the accessories |
| 13 | BENA | Power supply to headset adapter |
| 14 | VF | Programming voltage for FLASH |
| 15 | DCLK | DBUS data clock |
| 16 | VCHAR | Battery charging voltage |