Abstract: The antenna device has an antenna wire loop which, accompanied by the formation of two electrically outer (1,3) and one electrically central partial loop (2), is twice twisted by in each case 180.degree.. One of the two electrically outer partial loops (3) is geometrically positioned between the electrically central partial loop (2) and the other electrically outer partial loop (1). An impedance element (11) is connected between two connecting points (9,10) located at the entrance and exit of the geometrically central partial loop. The antenna device according to the invention has a very balanced characteristic and in the case of an appropriate choice of its parameters, behaves at the resonant frequency of the tags to be detected in the same way as an antenna with approximately 2 to 21/2 partial loops.

Abstract: A system for electronic safeguarding against burglary, or for monitoring, having a signal emitter and a receiver for receiving signals from a resonance label if the label is located in the zone of emitted signals. The system is adapted for use in stores, such as department stores, to detect unauthorized removal of items that carry a resonance label. The receiver evaluates the received signals to trigger an alarm signal upon detection by a receiver of a signal from a resonance label. Plural emitter-signal pairs are provided in which the respective emitter signals are wobbled at staggered frequencies within a broad frequency band. The emitter is also operative to emit and inoperative not to emit periodically only during alternating time phases and the receiver evaluates signals received by it for triggering the alarm only during the intervals between the signal emitting state of the emitter.

Abstract: A resonance label (1) comprises an insulating support layer (4) having two sides (2, 3). A first conductor is on one side (3) of the insulating supporting layer (4) and forms a capacitor plate (6b) and an induction coil (5) having a number of individual turns spaced apart from each other. A second conductor is on the other side (2) of the insulating supporting layer (4) and forms another capacitor plate (6a) so as to define a resonant circuit. At least one of the first and second conductors includes two adjacent conductor areas (6a, 7d) which are spaced apart at a distance (a) from each other closer to one another than the spacing between the individual turns of the induction coil (5). The distance (a) between the adjacent conductor areas (6a, 7d) defines a desired breakdown point (8) on the respective side (2) of the insulating support layer (4).

Abstract: An apparatus for the detection of labels used for preventing theft of goods and provided with an electric resonant circuit [(21) and] having a resonant frequency [(fr)] in the MHz range [comprises] has a transmitter [(1)] and a receiver [(2)]. The transmitter [(1)] generates a transmitting signal sequence, whose frequency is wobbled in wobble cycles over and beyond the given resonant frequency of the labels and [radiates] which is radiated by means of a transmitting antenna [(11)]. Signal generation in the transmitter [(1)] takes place digitally and with coinciding phase position with respect to each wobble cycle. In the receiver [(2)] the signals received by means of a receiving antenna [(12)] are scanned and digitized synchronously with signal generation in the transmitter [(1)]. From the digitized signal values of n wobble cycles a background is formed and subtracted from the digitized signal values of the in each case last wobble cycle.

Abstract: An apparatus for the detection of labels (21) used for preventing the shoplifting of articles (20) and which are provided with an electrical resonant circuit having a resonant frequency in the MHz range, comprises several pairs of transmitting and receiving antennas (8 to 13), which in each case bound passages (5 to 7) to be monitored. The transmitting antennas (8, 10, 12) of the pairs in each case radiate electromagnetic waves, whose frequency is wobbled in wobble cycles over the predetermined resonant frequency of the labels. The wobble cycles of all the pairs are synchronized with one another. To the receiving antenna (9, 11, 13) of each pair is connected a receiving circuit (17 to 19) detecting the presence of a label. For simplifying the installation, the invention proposes that the h.f.-oscillations radiated as electromagnetic waves by means of the transmitting antennas are generated by decentralized h.f.

Abstract: A process and circuit device for the deactivation and subsequent proof of a resonance label which has a resonant circuit with a certain Q factor and a certain frequency. The resonant circuit is energized with and disabled by a deactivation energy during deactivation. During deactivation, time is divided into a continuous alternating sequence of first and second time periods which directly follow one another. A transmission antenna transmits a deactivation energy during each of the first periods of time in the form of a sequence of separate deactivation impulses to cause the resonant circuit of the resonance label to oscillate in a resonant mode. The height and the width of each of the deactivation impulses and the number of the deactivation impulses within the impulse sequence are such that the impulse sequence delivers sufficient energy to deactivate the resonance label. The transmission is stopped and the transmission antenna is disabled for each of the second periods of time.

Abstract: A process and circut device for the deactivation and subsequent proof of a resonance label which has a resonant circuit with a certain Q factor and a certain frequency. The resonant circuit is energized with and disabled by a deactivation energy during deactivation. During deactivation, time is divided into a continuous alternating sequence of first and second time periods which directly follow one another. A transmission antenna transmits a deactivation energy during each of the first periods of time in the form of a sequence of separate deactivation impulses to cause the reosnant circuit of the resonance label to oscillate in a resonant mode. The height and the width of each of the deactivation impulses and the number of the deactivation impulses within the impulse sequence are such that the impulse sequence delivers sufficient energy to deactivate the resonance label. The transmission is stopped and the transmission antenna is disabled for each of the second periods of time.