Normal Operation - Gasoline Engine
WARNING: This page is about a different car, the 2009 Ford Econoline. However, it is still accessible from the selected car via links, so may be relevant.
The PCM sends a signal through circuit VES10 (WH) to the speed control switches, which passes through the clockspring. The signal return is sent to the PCM through circuit RES08 (GN/BN) and the clockspring. When the brake pedal is applied, the stoplamp switch sends a voltage signal to the PCM on circuit CCB08 (VT/WH) to deactivate the speed control if engaged.
The speed control deactivator switch (part of the stoplamp switch) interrupts circuit CES09 (VT/OG) removing the voltage signal to the PCM when the brake pedal is applied. This is a redundant signal to the PCM.