System for exchanging information between a portable object such as a key and an exchange device

摘要

A system is provided for exchanging information between a portable object, such as a key, and an exchange device, the latter being installed in a lock and transmitting a modulated carrier. The key comprises circuits for demodulating the modulated carrier received and restoring a first signal representative of the information transmitted by the exchange device, as well as processing circuits receiving the first signal and generating a second signal representative of the information to be transmitted. The second signal causes an impedance to vary suddenly so that the load seen by the exchange device varies and The information is thus transmitted thereto. The impedance is adapted in addition as a limiter. A clock signal is obtained, from the modulated carrier, by clipping, as well as a supply voltage by rectification and regulation.