Improvements in or relating to Vehicle Identification Systems.

摘要

The system may be applied to personal identification cards or the identification of baggage in automatic sorting apparatus and provides a key which employs passive components only in its structure. The "key" includes a responder circuit which receives energy radiated from an interrogation unit with data transmitted back to the interrogation unit using energy received from the unit, and effected at a carrier frequency derived from the carrier frequency of the transmission from the interrogation unit. The responder frequency is derived by multiplication or division of the frequency of the interrogation signals, with the circuitry permitting the system to be used in non-vehicular applications.