Function

The infrared remote control can only be operated with the transmitter belonging to the vehicle since the transmitter and the control module installed in the vehicle are matched to one another.

The transmitter transmits the transmitter signal to the receiver as an infrared light beam. The receiver receives the light beam, filters out light from external sources, amplifies the transmitter signal and passes it onto the control module via a control line.

The transmitter signal consists of a fixed code which is additionally coded by a computer. This additional coding changes with each operation. It is thus not possible to decode the transmitter signal.

The control module decodes the transmitter signal and, if the fixed code is correct, operates the central locking, the convenience feature and the anti-theft alarm system. At the same time the control module adjusts to the next transmitter signal and blocks the previous transmitter signal.

If the transmitter is operated outside the reception range, the current transmitter signal changes in the transmitter but not in the control unit.

When the transmitter is again used in the reception range, the transmission signal of the transmitter does not agree with that expected by the control module. However since the control module can calculate 250 further operations of the switch, it adjusts to the current transmitter signal.

If the transmitter has been operated outside the reception range more than 250 times, the transmitter must be resynchronized.

If a transmitter key is lost, the variable code portion of the transmission signal can be reset (desynchronized) by applying circuit 31 for a period of 30-40 seconds to the RCL diagnosis connection on the data link connector X11/4 when the ignition is ON.

Desynchronization can also be carried out with the pulse counter or the hand-held tester. As a result only the mechanical locking mechanism has to be replaced if a transmitter key is lost. Then all transmitter keys associated with this locking mechanism have to be resynchronized.

! As of 12/94 desynchronization can only be carried out with the Hand-held tester.