US Patent 7109851 Presence and recognition system

A transponder system for motor vehicle, used both as a RKE system and as a kill switch type safety system, is described herein. The transponder system includes an electronic lock assembly provided with a housing, an interrogator circuit and a coil antenna. The transponder system also includes an electronic key provided with a housing made of a slightly resilient material, a transponder circuit, and a coil antenna. The key assembly may be releasably mounted to the lock assembly since the housing of the key assembly is made of a slightly resilient material. Continuous interactions between the electronic lock and the electronic key are required for the continuous operation of the engine of the vehicle.