Display Lighting
The Saab Information Display (SID) module calculates a suitable value for the display lighting, using the rheostat value and the value for luminosity in the car's interior, which it receives from the light sensor. (Scheme 130)
When it is dark, it is the rheostat value that controls the lighting and when the light in the car's interior increases, it is the value for luminosity in the car's interior that takes over.
This results in good readability of the displays. The following lamps are controlled by the value for display lighting in the main instrument
- Trip Meter
- Odometer
Scheme 130
The car is equipped with an electronic speedometer. The ABS electronic control module continuously sends a speed signal to terminal 5 in the main instrument's electronic control module. The signal, which is a square wave, varies periodically between battery positive voltage and 0 V, 29 times for every wheel revolution. When the wheels are at standstill, the voltage could be either Battery positive voltage or 0 V. The electronic control module controls the speedometer, the odometer and the trip meter. The information is also available to other systems on pins 3 and 4. (Scheme 131)
