Onstar Sound and Radio Interface

The sound for the OnStar system is routed through the vehicles audio system. This is accomplished through a single circuit the Audio Mute Line. This circuit is pulled to ground signaling the vehicle radio to enter OnStar mode. At this time, the CIM sends sound through the speakers of the vehicle. While the radio is in OnStar mode the radio will mute all other media allowing for sound from the OnStar module. The volume control is set to a predetermined level when the OnStar system is activated. Once OnStar is active the volume level can be adjusted using the radio volume control.