This is the brains behind the brawn-Gear Vendors' overdrive electronic control, which allows precise control. Gear Vendors makes installation easy with detailed instructions and markings. Everything is color coded, so you can't miss. Yellow is the signal generator (speed sensor) at the speedometer cable. White energizes the overdrive solenoid (engaged or disengaged). Red is the main power on/off switch. Black is overdrive manual engagement. On the far left is the 12-volt main power source, which should be ignition-switched power (ignition "on" only, not accessory). Far right is ground. Mustangs & Fast Fords OC installed the module out of the way in this '65-'66 glovebox.