There's a four-ring 2.5mm stereo jack which provides connectivity to old-fashioned wired headsets.
The headsets used by Motorola smartphones (A780,A1200, ...) and the V-360 have a compatible configuration.
The headsets used by some Nokia phones (N95, ...) have the same jack but they are incompatible. For technical information about rewiring them visit Analog wired Headset Nokia.
base = ground speaker left (internal impedance 33R) to ground. (+jackinsert detection) speaker right (internal impedance 33R) to ground. tip = mic electret condenser type, to ground. bias (power for mic) 2K2 from +3.3v(wolfson codec) (+HoldButton shortcircuit to ground)
This matches the reported pinout for the Blackberry Pearl  but so far headset compatibility is unconfirmed.
Known working adapters
|Tester||Product||Seller||How it works|
|TimoJyrinki||MP35A||pc-mobile.net||Koss KSC-35 headphones, Altec Lansing inMotion iM4 speakers and car audio via AUX - all work great, if the mixer settings are changed like guided below. One can notice the lack of real quality sound with the headphones, but it's mostly fine for any casual listening. Definitely the output is not ideal/natural because of the high-pass filtering effect from the hardware issue and then artificially boosting low frequencies to compensate.|
You probably want to fix mixer settings to overcome the poor low-frequency output, see FreeRunner Hardware Issues for instructions.
To test Headset functionality
- Neo FreeRunner plus April Software Update
- FIC GTA02 battery
- SIM card
- Headset AP