Motor vehicle theft protection system

摘要

The system contains a portable transmitter (1) which transmits code information modulated by a carrier frequency and a receiver (2) in the vehicle which receives the code information, compares it with desired code information and generates a release signal if they coincide. The release signal activates/deactivates an immobiliser, opens/closes door locks and windows, and arms/disarms an alarm/warning device. The receiver has a first input stage (7) which demodulates the code signal from the fundamental oscillation of the received signal, and at least a second input stage (11) which demodulates the code signal from at least one harmonic of the received signal. The receiver has an evaluation unit in which a single code information set is formed by logically combining (19) the demodulated information.