The connector exists out of a combined 2,5- and 3,5 mm jack. The 2,5mm one is used as ground and for an external speaker, the 3,5mm one powers the PTT switch and microphone.
2,5mm jack connector
| Pin | Function |
|---|---|
| 1 (tip) | External speaker signal |
| 2 (ring) | GND |
| 3 (sleeve) | GND |
3,5mm jack connector
| Pin | Function |
|---|---|
| 1 (tip) | Not connected |
| 2 (ring) | Microphone (should be AC coupled) |
| 3 (sleeve) | PTT switch (pulled low to GND when pressed, otherwise floating) |
1 ------------------ /|
2,5mm jack | | SPEAKER
2 ---+---+--------+- \|
| | |
3 --- / |
/ ---| |
| | __
3 ------- --/ |
3,5mm jack ( | MICROPHONE
2 --------||---------\__|
+ 10µF
capacitor
3

