A new keyless entry system, for automotive security and comfort applications, has been developed. The system utilises a single chip transponder for vehicle immobilisation, keyless entry and remote control functionality. The transponder system can be embedded into a key fob or an ISO smart card. System security and communication speed is provided by an advanced anti-collision protocol in combination with sophisticated challenge response and uni-directional protocols. The system can be activated by using either a push-button transponder, where long range access to the vehicle is provided, or by touching an actuator near the door or trunk. Due to the inductive coupling between the transponder and the vehicle mounted antennas, the vehicle door or trunk opens on successful verification as if there were no locks. Additionally, inside the vehicle, the transponder can be used as an immobiliser.