Sharp PC-AL27 - Actius AL27 - Mobile Athlon 64 1.6 GHz Operation Manual page 70

Connecting Headphone
Use the headphone with an impedance of 8Ω or more. (32 Ω is recommended.)
Headphone/Audio
Output Jack
3
Stereo Mini Plug
Connecting Microphone
You can input sound using an external microphone connected to the microphone jack.
Use an electret condenser microphone with an impedance of 1.5kΩ through 2.4kΩ
and an allowable voltage of 2.5V.
Microphone Jack
Mini Plug
3-10
Headphone
Microphone