Deactivator Switch
WARNING: This page does not describe the selected car, but rather 14 other vehicles, including the 2004 Ford RV Cutaway, 2004 Ford Econoline, 2004 Ford E450 Super Duty, 2004 Ford Cutaway, and 2003 Ford RV Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
On vehicles with speed control, a deactivator switch is located underneath brake master cylinder as an additional safety feature. See Fig 1. Normally, when brake pedal is depressed, an electrical signal from brakelight circuit to speed control amplifier will turn off system. Under increased brake pedal efforts, deactivator switch mounted on master cylinder will open and remove power to speed control actuator clutch, releasing throttle independent of speed control amplifier.