Nokia headset / handsfree HDB-5 connector and schematics pinout

Wiring for the nokia 2.5mm 4-pole headset socket of Nokia 1100, 1101, 1110, 1600, 2100, 2300, 2500, 2650, 2652, 3210, 3310, 3330, 3410, 3510, 3510i, 3650, 3660, 5210, 6030, 6060, 6120, 6510, 6600, 7280, 7380 7650, 8210, 8310, 8800, 8850, 8890, 8910, 8910i cell phones (except some smartphones)

Pin	Name	Direction	Description
1	Tip		Speaker +
2	Ring 1		Microphone +
3	Ring 2		Speaker -
4	Sleeve		Microphone -

The answer/end button should be connected across the microphone connections.

Nokia 3210 handsfree / headset schematic

Nokia 8210 handsfree / headset schematic

Speaker is 30 Ohm