There are three components required for sensing garage door position. The first is the sensor itself (the Door Position Transmitter ), which is fastened to the door.

The Transceiver (Vehicle Interface Module) relays the signals from the door sensor(s) to the electrical wiring.

The indicator unit monitors the electrical wiring and displays the status of the garage door(s).

Thinking Home also monitors the signals on the electrical wiring and can log the information and act on it.