Original submission by T Apr 12th 2007:
Transmission Control Switch:
The TCS is found on late HX, late LX, HZ, VB, and UC's as part of the emission control.
The Transmission Control Switch (TCS) is mounted on the Gearbox and only permits Vacuum Advance to the Distributor when the vehicle is in Top Gear and the Engine is hot. The purpose of it is to reduce emissions during the warmup phase. The TCS is placed in series with the Cold Feed Switch (CFS) switch mounted on the Engine so that full Vacuum Advance is only available when the Engine is at or above 65 degrees in temperature and the Car is in Top Gear.
TCS On Manual Gearbox:The TCS is mounted under on of the Selector Levers on a Manual Gearbox.
TCS On Trimatic Gearboxes:The TCS is mounted on the nearside (passenger side) rear of a Trimatic Gearbox.
Cold Feed Switch:
The Cold Feed Switch from HX - VB. The Switch prevents Throttle controlled Vacuum from reaching the Distributor until the Engine is above 63 degrees Celsius by preventing the Vacuum Advance Control Solenoid from operating.