Abstract: An electromagnetic identfication system of the kind in which a transmitter generates an electromagnetic interrogation field in a detection zone. At least one passive responder is provided capable of disturbing the interrogation field. A detection circuit detects a disturbance of the interrogation field caused by a responder. The responder is a single receiver circuit which responds to the interrogation field which supplies energy to activate a digital encoding circuit having a binary-code defining circuit. The encoding circuit is arranged, in operation, through a switch to vary the electrical characteristics of the receiver circuit to generate a code signal that is detectable by the detection circuit. The encoding circuit is arranged to control the switch during the pre-determined periods of time for varying the electrical characteristics of the receiver circuit. A programmer is provided to modulate the transitter to generate a modulated interrogation field.

Abstract: An electronic identification system comprises at least one transmitter capable of generating an interrogation field in an interrogation zone and a plurality of responders capable of generating a pre-determined coded signal in response to an interrogation field. The signal can be detected by at least one receiver. According to the invention, the at least one responder has a receiver circuit adapted to be brought into a first mode in which the receiver circuit forms a tuned narrow-banded circuit and into a second mode in which the receiver circuit forms a broad-banded circuit.

Abstract: A system for the contactless exchange of data between a transceiver and a passive data carrier is described. A prior data carrier comprises at least one digital memory and at least one digital control device for the memory. In it, the data carrier has a single-coil receiver circuit connected to a controllable switch device. In operation, the data carrier provides, in response to an electromagnetic a.c. field generated by a transceiver, via at least one rectifier, supply power for active components of the data carrier and clock signals for the control of digital components of the data carrier. According to the present invention, in order to provide for the possibility of bi-directional data exchange between a transceiver and a passsive data carrier, and in general, to provide a universally applicable data exchange system of the contactless kind, the transceiver is equipped with a modulator for amplitude modulating the a.c. field.

Abstract: A detection system comprises at least one gate including transmitter means for forming a magnetic field and receiver means for receiving a signal transmitted by a detecting wafer provided with an oscillating circuit, wherein each gate comprises at least two spatial detection zones.

Abstract: A detection plate for an identification system, comprising a resonant circuit, a switching device, and coding means, characterized in that the coding means comprises a digital circuit and is arranged to receive, in operation, supply voltage from the resonant circuit via rectifier means.