Envoy 2WD V8-5.3L VIN P (2004)
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 vehicle
communication interface module (VCIM) by means of either a cellular microphone low reference circuit or a drain wire.
