OnStar® Microphone

The OnStar®, or cellular phone microphone, can be a part of the rearview mirror assembly, or on some vehicle lines, a separate, stand alone unit. In either case, the vehicle communication interface module supplies approximately 10 V to the microphone on the cellular phone microphone signal circuit, and voice data from the user is sent back to the vehicle communication interface module over the same circuit. A cellular phone microphone low reference circuit or a drain wire provides a ground for the microphone.