Samsung OG-I9020FSTTMB - Manual (Page 12)

Your phone and accessories 12
NSOG-1.0-104 Nexus S Owner’s Guide
Using the headset
The headset plugs into the phone’s 3.5mm headset jack.
You control the headphones’ volume with the phone’s Volume Up/Down button, and
with the applications on your phone (as described in the Android User’s Guide and in
the documentation for your applications).
Headphones
3.5mm headphone jack
Microphone