Entertainment System

The Entertainment System is controlled by several modules. The radio (IRC) is the radio head, containing the tape and single-disc compact disc (CD) player. The radio amplifier provides the power to drive several speakers. The antenna module controls the selection of the front and rear windshield antennas, and amplifies the resulting signal (FM mode). The CD changer (optional) is controlled by the radio, and sends its output to the radio amplifier. The Dash Integration Module (DIM) controls the function of the steering wheel controls. The radio amplifier also allows cellular telephone (if equipped) audio to be played through the speakers, if desired. These modules are linked in several ways. The radio, radio amplifier, DIM and cellular telephone module exchange operating information via Class 2 serial data. The CD changer and the radio exchange operating information via a dedicated E and C serial data line. Audio, antenna, interior light level and other signals are transmitted via dedicated circuits.

When the door is opened, one vehicle module, the DIM, is alerted, and sends out a wake-up message via Class 2 to the other modules. The radio and radio amplifier respond by turning on some portion of their functionality, regardless of ignition switch state or whether the radio is turned on or off. At some point, the chime function is requested via Class 2 serial data line. The radio responds by generating a chime signal, and sending it to the radio amplifier, which amplifies the signal and sends it to the left front speaker. When the radio is turned on, it sends a voltage to the antenna module, allowing the antenna module to turn on. If the radio is in AM mode, the radio antenna input is connected directly to the rear antenna (located in the back glass) only. If FM is selected, an additional enable signal is sent to the antenna module. This signal consists of two components: a DC status signal and the varying signal used by the radio. The antenna module responds by turning on the antenna module internal radio amplifier, and selecting between the front and rear antennas, depending on which is providing better reception. (This selection is determined by the signal strength being reported by the radio.) The signal is then amplified and sent to the radio. The radio amplifier always provides at least 10 dB of signal gain.

The radio uses the antenna input signal to create a stereo audio output signal, which is sent at the user-defined volume level to the radio amplifier. The radio amplifier amplifies the signal and sends it to the appropriate speakers. Tone, balance and fade information is sent by the radio via Class 2 serial data line and is received by the radio amplifier. Additional output processing is provided by the noise-canceling microphone. The microphone monitors interior ambient noise, and allows the radio amplifier to modify its output so that an enjoyable signal is always heard.

Some audio functions are available using the steering wheel controls. When a steering wheel control button is pressed, a specific resistance value is noted by the DIM. This results in a generated voltage, unique to the particular button. The DIM alerts the radio that the button has been pressed, and the radio responds, just as if the corresponding radio front panel button had been pressed. The tape player, as well as the in-dash CD player, disable the radio tuner and provide their output to the radio amplifier through the same circuitry as the tuner. The CD changer, if equipped, communicates with the radio via a dedicated E and C serial data line. When CD changer operation is selected, a message is sent to disable the radio output. The changer then sends its output directly to the radio amplifier, using a dedicated radio amplifier input circuit completely independent of the radio input to the radio amplifier.

When equipped with a cellular telephone, the radio signal may be muted, allowing the telephone audio signal to be heard through the speakers.

For a description of the RPO Code(s) shown in this image/article refer to the RPO Code List found at Vehicle/Application ID RPO Codes