Remote control key with transponder, function - GF80.30-P-4001-01A
WARNING: This page does not describe the selected car, but rather 42 other vehicles, including the 1999 Mercedes-Benz S600, 1999 Mercedes-Benz S500, 1999 Mercedes-Benz S420, 1999 Mercedes-Benz S320, and 1999 Mercedes-Benz CL600. However, it is still accessible from the selected car via links, so may be relevant.
When one of the buttons is pressed a radio frequency signal is transmitted from the remote control key via the RF antenna to the RF receiver module in the RF DAS control module (N54/3) (model 170) or radio frequency/infrared DAS control module (N54/4) (models 129/140) . This radio frequency signal contains the code stored in the remote control key. This code changes each time the control is actuated.
Models 129/140:
When one of the three keys is pressed an infrared signal is transmitted parallel to the radio frequency signal to the IR receiver in the left front door (A26/1) or right front door (A26/2).
The infrared signal ensures actuation of the central locking in the event of interference with the radio frequency signal.