| Pin | Name | Dir | Description |
|---|---|---|---|
| 1 | GND | - | Ground |
| 2 | SELF-SERVICE | in/out | Recognition/control battery charger |
| 3 | LOAD | in | Charging voltage |
| 4 | BATTERY | out | Battery (S25 only) |
| 5 | DATA OUT (TX) | out | Data sent |
| 6 | DATA IN (RX) | in | Data received |
| 7 | Z_CLK | - | Clock line for accessory bus. Use as DCD In data operation |
| 8 | Z_DATA | - | Data line for accessory bus. Use as CTS in data operation |
| 9 | MICG | - | Ground for microphone |
| 10 | MIC | in | Microphone input |
| 11 | AUD | out | Loudspeaker |
| 12 | AUDG | - | Ground for external speaker |
Siemens sl42, sl45 and sl45i and some others should have audio L, R and Gnd somewhere in these 12 pins (for their stereo mp3 player). Suggested that audio L is pin 2, audio R is pin 11 and audio Gnd is pin 12.