Abstract: A detection label for an anti-shoplifting system, comprises a housing (2) accommodating an electrical circuit (21) detectable by an electromagnetic interrogation field, a needle (1) for securing the detection label to an article to be safeguarded, and a locking device (4, 8, 9) for locking the needle. The housing includes a fixed clip (3) which together with the rest of the housing encloses a slot-like free space, a cavity (7) for receiving the tip of the needle (1) which is placed within the housing, an operating push button device (4, 6) for moving the needle towards the clip, and a guide bore (20) in a fabric clamp (6) for guiding the needle during its movement toward the clip.

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: 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: An electromagnetic detection system comprises a transmitter-receiver apparatus coupled to at least one antenna element to form an electromagnetic interrogation field in an interrogation zone defined at least in part by physical means. A plurality of responders is capable of generating a detectable signal under the influence of an interrogation field. According to the invention, at least one antenna element is a suitably formed structural element forming part of the physical means.

Abstract: A high frequency power circuit for energizing at least one gas discharge lamp with two filaments. The circuit is adapted to be supplied with power from a DC voltage source, and comprises semiconductor switching elements and control means for the semiconductor switching elements. The circuit also comprises a high frequency transformer having at least one primary winding which, in operation, is supplied with an AC voltage signal by the semiconductor switching elements. The transformer has at least one secondary main winding and secondary auxiliary windings. The secondary auxiliary windings, in operation, energize the filaments of the at least one gas discharge lamp. The control means are adapted to disconnect, in a stand-by mode, by at least one controllable switching means. The connection between the at least one secondary main winding and the at least one gas discharge lamp.

Abstract: In a detection plate, an electronic circuit capable of being activated by a suitable interrogation field to generate a pre-determined signal is provided with pin-shaped attachment means arranged so that the unauthorized detachment of the attachment means results in the interruption of an electrical conductor forming part of said electronic circuit. In the embodiment the detection plate is an earmark for animals and the attachment means includes a pin integral with the plate. The pin has a point which can be pushed through an animal's ear and the device can then be fastened on the other side of the ear. The pin includes a conductive loop which extends into the point and is connected to the electronic circiut of the plate.

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: A passage device for cattle comprising an opening closeable by two doors hinged around vertical hinge axes on either side of the opening. As viewed from the space accessible via the passage device, one door is openable only outwardly and the other door only inwardly.

Abstract: A cattle feeding station comprising two side walls between which an animal to be fed can be present, at least one end wall shutting off one end of the feeding station, a feeding trough located at the end, including an identification system for identifying an animal present in the feeding station and further including computer-controlled fodder dispenser. The end wall is formed at least substantially by the feeding trough, which is movable in such a manner that the end wall, under control of appropriate operating means, can be brought into a position shutting off the feeding station, wherein the trough is accessible to an animal present in the feeding station, and into at least one other position leaving the end of the feeding station concerned open and wherein the trough is inaccessible to an animal present in the feeding station.

Abstract: An electromagnetic detection system comprising transmission unit for producing in at least one first detection zone an electromagnetic interrogation field. The system includes a plurality of responders having attachment element for attachment to articles to be protected, each including a resonant circuit and when present in a detection zone, in response to the interrogation field, producing a signal. The system further includes a first detection adapted to detect a responder and, on detection of a responder, to produce a warning signal. According to the invention, the responders are designed in such a manner that when the attachment elements are removed or when a responder is damaged, at least one frequency determining parameter of the responder is changed in a predetermined manner. At least one second detection zone is provided wherein responders with the at least one changed frequency determining parameter can be detected.

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 holder for an electronic detection element, which is adapted for attachment about the neck or other part of the body of an animal to be detected by a band. The holder is provided with a cavity for receiving the detection element and with at least one clamping member for adjustably clamping a band end.

Abstract: A safety transformer with low coupling factor, which comprises at least one primary winding mounted on a spool and at least one secondary winding mounted on a spool, and a core including a first section cooperating with the primary winding(s) and a second section cooperating with the secondary winding(s). The first and second core sections have facing ends and all facing ends of these core sections are separated by an isolating means.

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: A DC-to-AC voltage converter for the supply of power to at least one load, comprising an input circuit and at least one output circuit galvanically separated from said input circuit, and a converter transformer. According to the invention a primary winding of the converter transformer is series-connected to a switching transistor, which series circuit arrangement is connected between a positive input terminal and a negative input terminal, with one or more resonance capacitors being connected in parallel with the collector-emitter circuit of the switching transistor and/or in parallel with said primary winding.

Abstract: A feeding box for cattle, in particular pigs, comprising a space enclosed by four upright walls, a fodder dispenser in said box or in one of the walls of the box, one of said walls having an access opening therein. The opening includes closure means lockable by means responsive to the presence in said box of a selected one of the cattle, and included in a control circuit also including the dosing motor of said fodder dispenser. It is also possible that the wall opposite to the wall containing the fodder dispenser has two openings, each of which includes said closure means, and in which case a partition gate in the box is arranged for rotation about a shaft disposed in the boundary plane between the two gates.

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.