Radio, Stereo, and Compact Disc: Description and Operation

CIRCUIT OPERATION

The Radio with a remote Radio Control Head and Remote Cassette/Equalizer or Compact Disc Player (optional) uses a Serial Data Line to coordinate the operation of several independent units into a sound system. The Serial Data Line allows each of the units to communicate with the others by digitally encoded pulse streams or serial data. Access to the data is available at the Data Link Connector (DLC). The data can be read by a bi-directional scan tool.

RADIO RECEIVER
The Radio Receiver incorporates most of the circuitry found in an ordinary Radio including the tuner and amplifier. Instead of manually operated controls, however, it utilizes a data input/output port to control its functions. Signals are sent to this port from the Radio Control Head. The Radio Receiver responds to these signals by adjusting its frequency, changing its output to the speakers and soon.

RADIO CONTROL HEAD
The Radio Control Head contains all the control switches and the display. It controls the Radio Receiver by sending signals to it, causing the Radio Receiver to adjust its output accordingly. The Radio Control Head displays the selected receiving frequency and other operating information.

CASSETTE/EQUALIZER (UX1)
The Cassette/Equalizer is used to provide two functions. The Equalizer portion modifies the Radio's response to each of the five audio frequency bands as selected by the operator. The required signals are sent to the Radio Receiver over a Data Line, similar to that described earlier. The cassette portion derives a signal from cassette tapes and sends this signal to the Radio Receiver which amplifies it and drives the speakers. In addition, a mute signal is sent from the Cassette/Equalizer to the Radio Receiver to switch its program source from the internal tuner to the Cassette Player. The Cassette signals are not encoded.

ILLUMINATION
The Radio Control Head and Cassette/Equalizer or Compact Disc Player utilize a Vacuum Fluorescent (VF) display to provide the vehicle occupants with time and sound system information. With the Radio turned on, the VF displays light to a fixed brightness. When the Park Lights or Headlights are turned on, battery voltage is applied to the Radio Control Head via the Radio Receiver from the "Lights on input." This lights on signal is sent to the Cassette/Equalizer or Compact Disc Player through the Radio Control Head. The VF display then dims to the present dimmer control setting. With the lights on, the Radio Control Head receives a Pulse Width Modulated (PWM) illumination signal from the Light Switch through the Radio Receiver. A PWM signal is then sent to the Cassette/Equalizer or Compact Disc Player from the Radio Control Head. These PWM signals control the VF illumination which varies as the dimmer control is adjusted.

The Radio Control Head buttons and face illumination is incandescent. They are illuminated when the lights are turned on, receiving power from the Panel Light input. The Radio Control Head incandescent illumination brightness is controlled by the variable voltage panel light input. The Cassette Player, Compact Disc Player and the Cassette/Equalizer buttons and face are also incandescent. They receive their illumination signal from the PWM signal that comes from the Radio Control Head. The brightness of the incandescent bulbs is controlled by this PWM signal.

CASSETTE PLAYER (UM6)
The Cassette Player derives a signal from cassette tapes and sends the signal to the Radio Receiver which amplifies it and drives the speakers. In addition, a mute signal is sent from the Cassette Player to the Radio Receiver to switch its program source from the internal tuner to the Cassette Player. The Cassette signals are not digitally encoded.

COMPACT DISC (U1C)
The Compact Disc Player operates similarly to the Cassette Player.