Cellet Black 2.5mm pin to 3.5mm Hole Adaptor with On/Off Switch Builtin Mic for Cellphone. microphone and send/receivebutton On/Off feature will only work with phones that arecompatiblewith such capability Indicates an incoming call even while you are listening tomusicon your phone or PDA. The music stops when you receive anincomingcall. Use your favorite pair of headphones to listen to music orwatchmovies on your device with the Cellet Stereo headsetadapter.