Abstract: This invention relates to a deactivating device for deactivating shoplifting detection labels of an electronic shoplifting detection system. These labels comprise a resonant circuit with a coil and a capacitor and the deactivating device comprises an antenna circuit comprising an antenna coil tuned with at least one capacitor to the resonant frequency of the resonant circuit. By means of this arrangement, sufficient energy can be induced in a resonant circuit of a label to effect electrical breakdown in the capacitor thereof. According to the invention, the antenna coil of the deactivating device is coupled, on the one hand, to a supply source and, on the other, to earth via a switch. Circuitry is provided for supplying at intervals control pulses to the switch in order to bring the switch into the conductive state.

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 electromagnetic identification and location system is described. The system comprises at least one interrogator which, in operation, generates an electromagnetic interrogation field by at least one antenna coil, and at least one responder which, in response to the electromagnetic interrogation field, generates a code signal in accordance with a binary code stored in a code circuit of the responder. The code signal can be recognized by an identifier. According to the invention, the responder is provided with a generator which, in response to the interrogation field, generates and transmits a pilot signal. The system further includes a position-sensitive antenna arrangement for receiving the pilot signal.

Abstract: A system for, checking the loading and unloading of a tanker having at least one tank provided with a metal connecting pipe adapted to be coupled via a coupling to one end of a hose having a coupling at two ends, which hose can be coupled to a metal connecting pipe of a storage tank. The hose used is provided with an electric conductor extending between the couplings for the dissipation of electrostatic charges and the chassis of the tanker is grounded. A first inductive coupling is effected between one of the connecting pipes and an interrogator of an electromagnetic identification system, and a second inductive coupling is effected between the other connecting pipe and a passive responder generating a coded signal in an interrogation field. Thus an interrogation field formed by the interrogator cooperates via the first inductive coupling, the one connecting pipe, the electric conductor of the hose, the other connecting pipe, and the second inductive coupling with the responder.

Abstract: The invention relates to a shoplifting detection system of the transmission type, suitable in particular for the use of high-frequency interrogating signals, in which system an electronic label provided with a resonance circuit can effect an electromagnetic coupling between at least two antenna coils, at least one of which is a transmitting antenna coil which, in operation, is fed with an A.C. interrogating signal from a transmitter circuit, and at least one other of which is a receiving antenna coil which supplies a received signal to a receiver circuit. According to the invention said receiver circuit comprises a phase-sensitive synchronous detector to which the received signal is supplied, and to which a reference signal is supplied of such a phase that a component in the received signal, caused by an electronic label, provides a maximum output signal of said synchronous detector, and a signal phase-shifted through 90.degree.

Abstract: A method of placing an electronic responder of an electromagnetic interrogation system or an antenna coil of an electromagnetic interrogator device in or near an electrically conductive article. An opening is made in the article, which is larger than the responder or antenna coil, and the responder or the antenna coil is mounted in registry with said opening. There is also provided a slit in the article, extending from the opening, said slit interrupting extraneous circular currents.

Abstract: An identification system for wireless electronic identification and data transmission, comprises a reading unit and at least one electronic label including a resonant circuit and carrying data stored in a memory device of the label, which data can be read wirelessly when the label is introduced into a high-frequency interrogation field formed by a transmitter of the reading unit. The reading unit includes a control device which, in operation, periodically switches the interrogation field on and off and in the time intervals when the field is switched off switches on a receiver capable of detecting a signal transmitted by a label. The at least one label includes a modulator which in the time intervals when the field is switched off can modulate the quality factor Q of the resonant circuit in dependence on the data stored in the memory device.

Abstract: A method and an apparatus for identifying articles moving along a surface, especially suitable for conditions in which the surface and/or the articles comprise comparatively much electrically conductive material. The articles are provided with electronic responders, each having two electrodes which are insulated from each other and in operation, face the surface. The surface is provided with corresponding electrodes connected to a transmitter/receiver device. When the electrodes of a responder are located opposite the electrodes of the transmitter/receiver device, an electric field is produced between these electrodes, enabling information transfer between the responder and the transmitter/receiver device.

Abstract: This invention relates to a method and a system for selectively filling or emptying a tank by a filling or discharging device for the tank. In accordance with the invention, a passive responder and an aerial element of an electromagnetic detection system are respectively provided in the vicinity of the inlet or outlet of the tank and on the part of the filling or discharging device cooperating with the tank inlet or outlet. The aerial element forms part of a detection system for generating an electromagnetic interrogation field, which detection system generates a signal when detecting a responder. In one embodiment of the invention, the responder is a passive responder generating a uniquely coded signal by which the detection system identifies the responder.

Abstract: An electromagnetic detection system is described which, in operation, in a detection zone, by means of at least one transmission antenna coil, generates a swept-frequency interrogation field capable of being at least partly absorbed by a responder comprising a tuned circuit, if such responder is present in the detection zone. Detection means are provided, coupled with the transmission antenna coil to detect such absorption. According to the invention the detection means comprises means for eliminating spurious frequencies located outside the band of the swept frequency, said means comprising a mixer including a first input to which a signal from the transmission antenna coil is supplied, and a second input to which the output signal from a sweeper feeding the transmission antenna coil is supplied, and including an output connected with a low-pass filter.

Abstract: A detection wafer with a non-linear circuit for an electromagnetic detection system wherein two different transmission frequencies are used, comprising a resonant circuit connected to a non-linear element forming from the transmission frequencies, a third frequency to be detected. The non-linear element forms part of an amplifying semiconductor circuit connected to a supply battery and having an input circuit coupled to the resonant circuit, and an output circuit comprising a coil magnetically coupled to the coil of the resonant circuit, the resonant frequency bandwidth of the resonant circuit comprising both transmission frequencies and the frequency to be detected.

Abstract: In an electronic detection system comprising a transmitter for generating an interrogation field, said transmitter being coupled with at least one transmitting antenna coil; a responder with a receiving coil and a transmitting coil for transmitting a signal in response to said interrogation field; and a receiver-and-detector coupled with at least one receiving antenna coil for receiving and further processing the signal transmitted by said responder; the improvement which consists in that said receiving coil and said transmitting coil of said responder are arranged in parallel to each other, and that said responder comprises a frequency divider connected between said receiving and transmitting coil and arranged to divide the signal frequency received by a factor N.gtoreq.4.

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.