EP0919002A1 - Systeme de securite contre les vols a l'etalage - Google Patents

Systeme de securite contre les vols a l'etalage

Info

Publication number
EP0919002A1
EP0919002A1 EP97938355A EP97938355A EP0919002A1 EP 0919002 A1 EP0919002 A1 EP 0919002A1 EP 97938355 A EP97938355 A EP 97938355A EP 97938355 A EP97938355 A EP 97938355A EP 0919002 A1 EP0919002 A1 EP 0919002A1
Authority
EP
European Patent Office
Prior art keywords
signal
frequency
marker
interrogation zone
modulation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP97938355A
Other languages
German (de)
English (en)
Inventor
Jon Neal Weaver
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US08/699,880 external-priority patent/US5703566A/en
Priority claimed from US08/878,239 external-priority patent/US5900816A/en
Application filed by Individual filed Critical Individual
Publication of EP0919002A1 publication Critical patent/EP0919002A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2405—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting characterised by the tag technology used
    • G08B13/2408—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting characterised by the tag technology used using ferromagnetic tags
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
    • G01V3/10—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils
    • G01V3/104—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils using several coupled or uncoupled coils
    • G01V3/105—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils using several coupled or uncoupled coils forming directly coupled primary and secondary coils or loops
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2465—Aspects related to the EAS system, e.g. system components other than tags
    • G08B13/2468—Antenna in system and the related signal processing
    • G08B13/2471—Antenna signal processing by receiver or emitter
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2465—Aspects related to the EAS system, e.g. system components other than tags
    • G08B13/2468—Antenna in system and the related signal processing
    • G08B13/2474—Antenna or antenna activator geometry, arrangement or layout
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2465—Aspects related to the EAS system, e.g. system components other than tags
    • G08B13/2488—Timing issues, e.g. synchronising measures to avoid signal collision, with multiple emitters or a single emitter and receiver

Definitions

  • This invention relates to electronic article surveillance (EAS) systems. These systems are often used to detect shoplifters or otherwise monitor the movements of tagged articles.
  • the EAS systems of the type to which the subject invention is directed are generally employed to detect the presence of a magnetic marker in a magnetic field.
  • Such systems thus include a device, for example a generating coil, for generating the magnetic field, and another device, for example a receiving coil, for detecting signals generated when a marker is passed through the field.
  • EAS systems must comply with the rules of various agencies, e.g. the Federal Communications Commission. These agency rules can, for example, limit the amount of spurious emissions and the amount of electromagnetic interference (EMI) allowable.
  • EMI electromagnetic interference
  • the performance requirements of EAS systems can include limitations on the number of false alarms from noise or metallic objects, transmission energy, and an ability to control large interrogation zones.
  • Current EAS systems based on low frequency electromagnetic transmission can not meet all of these performance requirements while simultaneously satisfying the spurious emissions and EMI limitations, due to the rapid attenuation of the transmitted signal.
  • Important considerations in the design of EAS systems include, for example, power consumption of the system, cost of the system, signal-to-noise ratio of the received signal, and sensitivity to a marker in the detection field.
  • Factors which may influence the signal-to-noise ratio and sensitivity to a marker in the field may include coupling of the generated magnetic field and/or marker generated fields in the receiver, metallic objects in the vicinity of the EAS system, spurious emissions, and electromagnetic interference. Improving the signal-to-noise ratio and sensitivity to a marker in the field generally involves increased power consumption of the EAS system transmitter and/or receiver circuitry.
  • Prior disclosed EAS systems have utilized pulsed transmitter signals and corresponding detection of the signal generated by a marker located in the magnetic field produced by the transmitter.
  • both electromagnetic (EM) and radio frequency (RF) EAS systems have been disclosed which utilized a pulsed transmitter signal. These systems have received, during the "off cycle of the transmitter signal, the signal generated by a marker due to the marker's response to the transmitter signal generated du ⁇ ng the "on" cycle of the transmitter In these systems, the pulsing of the transmitter resulted in somewhat better signal to noise ratios. However, no attempt was made to detect modulation as an indication of the presence of a marker.
  • p ⁇ or EAS systems for example, in U.S. Patent Nos. 4,710,752 and
  • the subject invention pertains to novel Electronic Article Surveillance (EAS) systems and methods of electronic article surveillance which are able to detect tagged articles with, for example, reduced incidence of false alarms in the presence of noise, lower power consumption, and lower costs than current systems.
  • EAS Electronic Article Surveillance
  • the subject invention allows significant improvement m noise reduction and greatly increased sensitivity to a marker in the detection field.
  • the EAS system of the subject invention utilizes an amplitude modulated transmitter earner signal created by an electromagnetic generator and single coil When a soft magnetic marker is brought into the transmitter field, the marker generates a signal.
  • This signal generated by the marker contains harmonics of the transmitter earner signal which are amplitude modulated at the same frequency as the transmitter modulation signal.
  • the marker signal contains harmonics of the transmitter carrier signal which are modulated at frequencies which are harmonics of the transmitter modulation signal Accordingly, the receiver coil and receiver signal processor of the subject EAS system can receive the signal generated by the marker
  • the receiver demodulates the received harmonics of the transmitter earner signal and detects the modulation having the same frequency as the amplitude modulation signal as an indication that a marker is present. In a more preferred embodiment, the receiver demodulates the received harmonics of the transmitter carrier signal and detects the modulation havmg frequencies which are harmonics of the amplitude modulation signal as an indication that a marker is present.
  • the subject EAS system can have a higher signal-to-noise ratio than other systems utilizing amplitude modulated transmitted signals
  • the subject EAS system detects the modulated harmonics and/or the harmonics of modulation generated by the marker, where modulated harmonics and/or harmonics of modulation are only present when a marker, or similar object, is present in the detection field.
  • the subject invention provides novel Electronic Article Surveillance (EAS) systems which are able to detect tagged articles with a reduced incidence of false alarms even in wide interrogation zones and in the presence of noise.
  • EAS Electronic Article Surveillance
  • the systems of the subject invention can operate at lower power than current systems.
  • an electromagnetic field is created as a superposition of two individual fields generated with two transmitters, close in frequency and approximately equal m amplitude
  • a ferromagnetic marker When a ferromagnetic marker is brought into the interrogation zone, I e., into the magnetic field, the marker generates amplitude modulated harmonics of each of two individual fields, wherein each marker generated amplitude modulated harmonic is phase shifted
  • the presence of a marker is then determined by detecting the presence of a phase shift m an amplitude modulated harmonic. The detection of this phase shift by the receivers, greatly reduces the probability of detecting a random noise signal, as well as minimizes false alarms due to ferrous objects having greatly different phase responses from that of an intended marker.
  • each transmitter and its associated receiver can be separated by the interrogation zone.
  • Figure 1 shows a schematic representation of an embodiment of an EAS system transmitter and receiver in accordance with the subject invention.
  • Figure 2A shows one representation of an amplitude modulated transmitter signal in accordance with the subject invention.
  • Figure 2B shows a representation of an amplitude modulated harmonic produced by a marker located in the field produced by the amplitude modulated transmitter signal of figure 2A, in accordance with the subject invention.
  • Figure 2C shows a representation of a modulation waveform which can be used in accordance with the subject invention.
  • Figure 3 shows a schematic of an embodiment of an EAS system with the transmitter modulation frequency locked to the receiver modulation filter in accordance with the subject invention.
  • Figure 4 shows a schematic representation of an embodiment of an EAS system havmg two transmitter-receiver pairs, in accordance with the subject invention.
  • Figure 5A shows a schematic of an EAS system having two transmitter-receiver pairs wherein the transmitters are turned on and off, out of phase, by a clock.
  • Figure 5B shows an example of clock, transmitter, receiver, and modulation signals in accordance with the EAS system shown in Figure 5A.
  • the subject invention pertains to novel Electronic Article Surveillance (EAS) systems and methods of electronic article surveillance which are able to detect tagged articles with reduced incidence of false alarms m the presence of noise, lower power consumption, and lower costs than current systems.
  • EAS Electronic Article Surveillance
  • the subject invention allows significant improvement in noise reduction and greatly increased sensitivity to a marker in the detection field.
  • the EAS system of the subject invention utilizes an amplitude modulated transmitter signal created by, for example, an electromagnetic generator and coil
  • an amplitude modulated transmitter signal created by, for example, an electromagnetic generator and coil
  • the marker When a soft magnetic marker is brought into the transmitter field, the marker generates a signal
  • This signal generated by the marker contains harmonics of the transmitter earner signal which are amplitude modulated at the same frequency as the transmitter modulation signal
  • the marker signal contains harmonics of the transmitter earner signal which are modulated at frequencies which are harmonics of the transmitter modulation signal. Accordingly, the receiver coil and receiver signal processor of the subject EAS system can receive the signal generated by the marker.
  • the receiver demodulates the received harmonics of the transmitter earner signal and detects the modulation having the same frequency as the amplitude modulation signal as an indication that a marker is present. In a more preferred embodiment, the receiver demodulates the received harmonics of the transmitter earner signal and detects the modulation having frequencies which are harmonics of the amplitude modulation signal as an indication that a marker is present.
  • the subject EAS system can have a higher signal-to-noise ratio than other systems utilizing amplitude modulated transmitter signals.
  • pnor radio frequency EAS systems utilizing amplitude modulated transmitters attempt to detect the modulated field produced by the marker, in the presence of coupling of the modulated field produced by the transmitter in the receiver.
  • the modulation is present whether or not a marker is present in the detection field, due to coupling in the receiver.
  • these other amplitude modulated systems must then differentiate the signal due to the presence of a marker and the signal due to coupling of the transmitter generated field the receiver.
  • the modulation itself is not a problem. This is because modulated harmonics and/or harmonics of the modulation generated by a marker are detected, which are present only when a marker is present.
  • the subject invention improves on previous designs by maximizing a modulated signal from the marker while the transmitter is generating its highest (peak) output signal and, simultaneously, reducing the power consumption of the system when the transmitter is generating its lowest output signal.
  • modulating the transmitter output signal can further enhance detection by reducing the shielding of the marker by the transmitter This shielding effect occurs when the transmitter output signal is at a maximum and can be reduced or eliminated when the transmitter output signal is reduced.
  • the minimum transmitter output signal magnitude is between about 30 percent and about 50 percent of the maximum transmitter output signal magnitude.
  • the transmitter signal drops to about 30 to about 50 percent of the maximum, the marker is no longer shielded and can be detected, thus enhancing detection.
  • This effect can also be observed when the transmitter is pulsed on and off if the ns g and/or falling edge(s) of the pulse train reside at a value of about 30-50 percent of the maximum value for a sufficient duration, thus allowing detection of a marker near the transmitter coil.
  • the subject invention allows the use of smaller markers, fewer loops on the transmitter antenna coil, and/or more peak power with the same components as previous EAS systems.
  • the use of smaller markers can reduce the expense of marking items, as well as allowing more effective marking.
  • the smaller markers can be more discretely appended to merchandise Transmitter coils having fewer loops are less expensive to build, lighter, and more compact. It is a matter of design choice as to which of these advantages to exploit.
  • by detecting modulation of harmonics of the transmitter earner signal the effects of coupling of unwanted signals from the transmitter in the receiver are minimized, creating a very high signal to noise ratio.
  • the subject EAS system can alternate the modulation frequency from a first frequency to a second frequency in order to produce a dual (two tone) modulation which is extremely difficult to duplicate in ordinary circumstances and environments. This reduces the probability of false detections.
  • different modulation frequencies are accomplished with the transmitter modulation frequency locked to the receiver modulation filter.
  • This circuitry can act independently from the general EAS system frequency or circuitry.
  • a specific embodiment of the subject invention can compnse transmitting generator 1 and transmitting coil 2 for generating a magnetic field in the interrogation zone, and detector 3 and receiving coil 4 for receiving and detecting magnetic fields generated by a marker located in the interrogation zone.
  • Figure 2A shows one representation of an amplitude modulated transmitter signal in accordance with the subject invention.
  • This transmitter earner signal can have many different waveform shapes, for example sinusoidal.
  • the modulating signal can also have many different waveform shapes and/or parameters.
  • the amplitude modulating signal can have equal duration on and off cycles, or an on cycle to off cycle ratio which differs from one.
  • the off cycle can be set to turn the transmitter signal completely off or set to lower the magnitude of the transmitter signal.
  • the amplitude modulating signal can vary between a peak value and some fraction, for example 50 percent, of peak value.
  • Figure 2B shows a representation of a signal generated by a marker present in the interrogation zone, which is a harmonic of the transmitter carrier signal modulated by the modulating signal of Figure 2C.
  • Detector 3 can receive and demodulate the modulated harmonic generated by a marker and utilize the modulation as an indication of the presence of a marker.
  • a further embodiment of the subject invention is particularly advantageous when extremely high noise environments are encountered.
  • the embodiment described in Example 1 can be utilized with additional circuitry added to allow the modulation frequency to alternate among at least two frequencies.
  • the frequency of the modulating signal can alternate between a first frequency and a second frequency m order to produce a dual (two tone) modulation This two tone modulation is unlikely to be duplicated by noise, thus lower the probability of false detections.
  • different modulation frequencies can be accomplished by, for example, locking the transmitter modulation frequency to the receiver modulation filter
  • this circuitry can act independently from the general EAS system circuitry.
  • each pair can comprise a transmitting coil 11, 12 and a receiving coil 9, 10.
  • transmitting coil 11, preferably of a single coil design is connected to a first field generator (transmitter) 13, and transmitting coil 12, preferably of a single coil design, is connected to a second field generator (transmitter) 16.
  • transmitter coil 11 is receiver coil 9, which can be parallel to transmitter coil 11 and separated from transmitter coil 11 by the interrogation zone.
  • receiver coil 10 which can be parallel to transmitter coil 10 and separated from transmitter coil 12 by the interrogation zone.
  • Receiver coil 9 is connected to detector 15, which employs circuitry to detect a marker
  • receiver coil 10 is connected to detector 14 which employs circuitry to detect a marker.
  • transmitters 13 and 16 may be switched on and off out of phase with each other, for example, by clock 20. Accordingly, when transmitter 13 is on, transmitter 16 is off and vice versa.
  • transmitter 16 when transmitter 16 is on, coil 12 generates an appropriate time- varying magnetic field in the interrogation zone, and when transmitter 13 is on, coil 11 generates an appropriate time-varying magnetic field in the interrogation zone.
  • the coil pairs can be separated further, for the same power output, such that each pair only covers one half of the interrogation zone.
  • the marker when a marker is located in the half of the interrogation zone closest to coil 12, the marker will produce an amplitude modulated signal which can be detected and demodulated by detector 14. Likewise, when a marker is located in the half of the interrogation zone closest to coil 11, the marker will produce an amplitude modulated signal which can be detected and demodulated by detector 15. It can be observed, that this embodiment allows various advantages, for example, lower power consumption, smaller transmitter coils, and/or a wider interrogation zone.
  • coil 11 and coil 12 can be modulated at different frequencies.
  • the signal from the marker can be detected and demodulated, with the amplitude modulation indicating the presence of a marker.
  • coil 11 and coil 12 can be modulated at different frequencies and the signal from a marker can be detected and demodulated, with the phase modulation used as an indication of the presence of a marker.
  • coil 11 and coil 12 can be connected to transmitter 13 and 16, respectively, wherein the transmitters 13 and 16 operate at different frequencies.
  • the transmitters 13 and 16 operate at different frequencies.
  • operating transmitters 13 and 16 at different frequencies can create an amplitude and phase modulated harmonic signal produced by a marker.
  • transmitters 13 and 16 can be switched on and off, or pulsed, simultaneously in order to create an additional amplitude modulation within the harmonic generation of the marker.
  • the result of amplitude modulation, or switching on and off, of the two earners and the phase modulation created by two different transmitter frequencies creates a marker harmonic signal having amplitude modulation at a specific frequency and a phase modulation at another unique frequency
  • the combination of the amplitude modulation at a specific frequency and the phase modulation at another unique frequency are not easily realized by random noise sources.
  • coil 11 can be dnven at 1000 Hz and coil 12 can be dnven at 1020 Hz, creating a marker signal with a phase modulation of 20 Hz or a multiple of 20 Hz.
  • a marker signal can contain a 6 Hz amplitude modulation of the marker generated harmonics of the transmitter signals. Accordingly, phase detection and narrow band filtering of the 20 Hz, or multiple of 20 Hz, signal produce a 20 Hz phase modulation signal which can indicate the presence of a marker in the interrogation zone.
  • amplitude detection and narrow band filtenng of the 6 Hz amplitude modulation results in a 6 Hz amplitude modulation signal which can also indicate the presence of a marker m the interrogation zone.
  • both the 20 Hz phase modulation signal and the 6 Hz amplitude modulation signal can be detected and used as an indication of the presence of a marker wherein combination of both modulation signals is extremely difficult to replicate in any noise environment and therefore can reduce false alarms.
  • the switching of transmitters on and off allows the use of smaller transmitter coils without reducing peak transmit field intensities.
  • each transmitter is of a single coil design.
  • An EAS system of the subject mvention used to detect a marker in the interrogation zone is shown, schematically, in Figure 1
  • the system of the subject invention can compnse a pair of antenna arrays each compnsing a transmitting coil 11, 12 and a receiving coil 9, 10.
  • transmitting coil 11 preferably of a single coil design, is connected to a first field generator 13, that can produce an output equivalent to less than about 50 Watts rms, and preferably less than about 25 Watts rms.
  • the frequency of a transmitting coil is approximately 1 kHz (FI).
  • FI kHz
  • a receiver coil 9 which is parallel to the transmitter coil 11 and separated from transmitter coil 11 by the interrogation zone.
  • the receiver coil 9 is connected to detector 15, which employs circuitry to detect a marker
  • a second transmitter coil 12 preferably of a single coil design, is connected to a second field generator 16, which is about 3 to about 50 Hertz lower or higher m frequency (F2) than the frequency (FI) produced by the first field generator 13.
  • the receiver coil 10 is connected to a detector 14, which is substantially equivalent to detector 15. Accordingly, there are components of two transmitter-receiver systems that operate at slightly different frequencies with associated transmitters and receivers separated by an interrogation zone.
  • the ratio of the amplitudes of the transmit fields is in the range of about 1 : 1 to about 1.5: 1, and preferably about 1.1.
  • a marker passing through the interrogation zone produces harmonics which are amplitude modulated at a rate determined by the difference in transmission frequency [F1-F2] and which are phase shifted due to inherent material properties of the marker Since all generators produce harmonics of the transmitted fundamental, the receives coils 9 and 10 are positioned away from their associated transmitters on opposite sides of the interrogation zone
  • the detector 14 can utilize narrow band harmonic filters to minimize out-of-band signals such as the harmonics being transmitted by the adjacent coil 11. Detector 15 functions m an equivalent manner.
  • In-band signals passed through harmonic filters in each detector are demodulated and the modulation compared m phase with a reference signal. Since both detectors and their associated generators are phase locked together, phase compa ⁇ son is relatively simple and when present conditions are met, an alarm is activated.
  • the reference signal, both detectors, and both transmitters are phase locked

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Computer Security & Cryptography (AREA)
  • Signal Processing (AREA)
  • Remote Sensing (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geology (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geophysics (AREA)
  • Burglar Alarm Systems (AREA)

Abstract

La présente invention se rapporte à des procédés et à un dispositif permettant de déceler la présence d'un marqueur magnétique souple dans une zone d'interrogation. On génère un champ électromagnétique basse fréquence, au moyen de générateurs à deux fréquences, qui fait engendrer par le marqueur magnétique un déphasage de la modulation des harmoniques de transmission. Il est facile de distinguer ces signaux de ceux issus d'alliages ferreux ou de ceux associés à un bruit. Cette invention fait usage d'un signal de porteuse modulé, généré dans une zone d'interrogation. Les harmoniques modulées du signal de la porteuse sont détectées lorsqu'un marqueur est présent dans la zone d'interrogation. La modulation détectée peut être à la même fréquence que celle du signal de la porteuse ou être une harmonique de la modulation du signal de la porteuse. La détection de cette modulation permet d'obtenir des rapports signal-bruit relativement élevés et réduit par conséquent les risques de fausses détections.
EP97938355A 1996-08-16 1997-08-15 Systeme de securite contre les vols a l'etalage Withdrawn EP0919002A1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
US08/699,880 US5703566A (en) 1996-08-16 1996-08-16 Anti-shoplifting security system
US699880 1996-08-16
US878239 1997-06-18
US08/878,239 US5900816A (en) 1997-06-18 1997-06-18 Anti-shoplifting security system utilizing a modulated transmitter signal
PCT/US1997/014441 WO1998007052A1 (fr) 1996-08-16 1997-08-15 Systeme de securite contre les vols a l'etalage

Publications (1)

Publication Number Publication Date
EP0919002A1 true EP0919002A1 (fr) 1999-06-02

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP97938355A Withdrawn EP0919002A1 (fr) 1996-08-16 1997-08-15 Systeme de securite contre les vols a l'etalage

Country Status (3)

Country Link
EP (1) EP0919002A1 (fr)
AU (1) AU4070697A (fr)
WO (1) WO1998007052A1 (fr)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DK24798A (da) * 1998-02-23 1998-03-03 Tss Traffic Supervision System Fremgangsmåde til simultan AM-demodulering af data og signaler der opstår ved vekselvirkning med metal
US9427186B2 (en) 2009-12-04 2016-08-30 Endomagnetics Ltd. Magnetic probe apparatus
US10634741B2 (en) 2009-12-04 2020-04-28 Endomagnetics Ltd. Magnetic probe apparatus
JP6351639B2 (ja) 2013-03-11 2018-07-04 エンドマグネティクス リミテッド リンパ節検出のための低浸透圧溶液
WO2014140567A2 (fr) * 2013-03-13 2014-09-18 Endomagnetics Ltd. Détecteur magnétique
US9239314B2 (en) 2013-03-13 2016-01-19 Endomagnetics Ltd. Magnetic detector
US9234877B2 (en) 2013-03-13 2016-01-12 Endomagnetics Ltd. Magnetic detector
WO2016193753A2 (fr) 2015-06-04 2016-12-08 Endomagnetics Ltd. Matériaux et formes de marqueur pour localisation à marqueur magnétique (mml)
CN109658657A (zh) * 2018-12-11 2019-04-19 成都威图芯晟科技有限公司 信号发生方法、分析方法、检测方法、相应设备及系统

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Publication number Priority date Publication date Assignee Title
US3686564A (en) * 1970-10-08 1972-08-22 Westinghouse Electric Corp Multiple frequency magnetic field technique for differentiating between classes of metal objects
US3990065A (en) * 1975-02-20 1976-11-02 The Magnavox Company Theft detection system
US4710752A (en) * 1986-08-08 1987-12-01 Pitney Bowes Inc. Apparatus and method for detecting a magnetic marker
GB9302757D0 (en) * 1993-02-11 1993-03-24 Esselte Meto Int Gmbh Method and system for detecting a marker

Non-Patent Citations (1)

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Title
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Also Published As

Publication number Publication date
AU4070697A (en) 1998-03-06
WO1998007052A1 (fr) 1998-02-19

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