Cellular Phone Microphone: Description and Operation

ONSTAR(R) MICROPHONE

The OnStar(R), or cellular, microphone can be part of the rearview mirror assembly, or on some vehicle lines, can be a separate, stand alone unit. In either case, the microphone is supplied voltage on the cellular microphone signal circuit, while voice data from the user is sent back to the VCIM by means of either a cellular microphone low reference circuit or a drain wire.