Cellular Phone: Description and Operation

VEHICLE COMMUNICATION INTERFACE MODULE (VCIM)

The VCIM is a 3-watt cellular device that allows the user to communicate data and voice signals over the national cellular network. It is powered by a fused, battery positive voltage circuit, connected through vehicle wiring to the 3-button assembly and the radio, and attached by means of coax cables to the cellular and navigation antennas. Ground for the module is accomplished by means of dedicated circuits that are routed with body wiring systems to chassis ground points. The module houses two modems, one to process global positioning system (GPS) data, and the other for cellular information. Satellites orbiting earth are constantly transmitting signals of their current location, from which the OnStar(R) system is able to pinpoint its own location. The navigation antenna receives these GPS signals and provides the data to the VCIM to be processed. The VCIM communicates with the rest of the vehicle over the class 2 serial data bus. Ignition state is determined by the VCIM through class 2 messaging. The module also has the capability of commanding the horn, door lock/unlock and operating the exterior lamps using the class 2 serial data circuit. When an OnStar(R) keypress is made, a class 2 message is sent to the audio system to mute all radio functions and transmit OnStar(R) originated audio. After the audio system is muted, the OnStar(R) signals are transmitted to the audio system on the cellular telephone voice signal circuit, and returned to the module on the cellular telephone voice low reference circuit. The cellular modem connects the OnStar(R) system to the cellular carrier's communication system by interacting with the national cellular infrastructure. The module sends and receives all cellular communications over the cellular antenna and cellular antenna coax.

OnStar(R)
OnStar equipped (RPO UE1) vehicles use the radio amplifier and speaker system for voice communication from the OnStar operator to the vehicle. Voice communication from the vehicle to the OnStar operator is through the OnStar microphone and module, which is not a part of the radio system.

When OnStar begins operation, the radio volume is set to a preset level, autotone preset for OnStar becomes active and the fade control is adjusted to the full front speakers. The radio volume control can then be used to adjust the volume to a desired level.

The radio system and OnStar system are connected through the 12-way connector at the back of the radio. Left and right channel OnStar audio, mute control of radio functions by OnStar, and the audio signal ground are the circuits provided in the 12-way connector.

Disconnecting the 12-way connector from the radio will isolate the radio system from the OnStar system. Voice communication from the vehicle to the OnStar operator could be possible under this condition. However, the vehicle occupant will not be able to hear the OnStar operator.

If the vehicle is also equipped with OnStar(R), DVD audio will be interrupted during an OnStar(R) call. During an OnStar(R) call, the mute line is low, ground, and the AVI module relay switches to connect the OnStar(R) audio to the radio audio inputs. In OnStar(R) AUX mode, the radio displays AUX and the fade is fixed at full-front, balance control is fixed at center, and the tone control is fixed at a pre-set equalization.