EP0840266B1 - Device for monitoring a security element in an interrogation area - Google Patents
Device for monitoring a security element in an interrogation area Download PDFInfo
- Publication number
- EP0840266B1 EP0840266B1 EP97117103A EP97117103A EP0840266B1 EP 0840266 B1 EP0840266 B1 EP 0840266B1 EP 97117103 A EP97117103 A EP 97117103A EP 97117103 A EP97117103 A EP 97117103A EP 0840266 B1 EP0840266 B1 EP 0840266B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- computing
- signals
- control unit
- measured values
- signal
- 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.)
- Expired - Lifetime
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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
- G08B13/2465—Aspects related to the EAS system, e.g. system components other than tags
- G08B13/2482—EAS methods, e.g. description of flow chart of the detection procedure
-
- 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
Definitions
- the invention relates to a device for monitoring of an electronic security element in one Interrogation zone, consisting of a transmission device, the at least one periodic interrogation signal in the interrogation zone sends out, the interrogation signal the security element stimulates to send a detection signal, one Receiving device which receives the detection signal, and a computing / control unit that the by the Received device evaluates signals and at Identification of the security element an alarm triggers.
- EP 123 586 B suggested, in addition to two query fields with the Frequencies F1 and F2 in the kHz range a field with an im Hz range lying frequency F3 in the interrogation zone send.
- the low frequency query field causes the fuse element in time with this field of the Saturation in one direction to saturation in the other Direction is driven.
- the characteristic signal occurs therefore periodically with the frequency of the low frequency Field.
- the invention has for its object a device propose the recognition of articles related to electronically detectable security elements are improved within a query zone.
- the object is achieved in that the computing / control device the during a given period of time received signals recorded, based on the signals determines whether and if so with which period Interference signals occur and these interference signals from the received signals removed.
- This enables the device according to the invention, in addition to periodically occurring Interference signals of known origin also occur periodically Eliminate interference signals from sources of interference with unknown interference frequencies.
- Interference signals of known origin also occur periodically Eliminate interference signals from sources of interference with unknown interference frequencies.
- the computing / control device determines the periodic interference signal on the basis of the smallest resulting difference c (n) if the difference c (n) is smaller than a predetermined maximum value c max , which is a fraction represents the average interference signal.
- the interfering signal thus periodically determined is then from subtracted from the received signals.
- the measurement data are fixed with a predetermined time constant, which is an integer multiple f is the duration of one cycle of the surveillance system, updated.
- Fig. 1 shows a schematic representation of the Device 1 according to the invention for detecting a a securing element 2 provided Article 6 in one Query zone 3.
- Query zone 3 is composed of two in essentially parallel detector gates formed, the transmitter 4 and the Receiving device 5 included. Of course you can both devices 4, 5 also in a detector gate be housed.
- the control of the monitoring device 1 and the evaluation of the measured values takes place by means of the computing / regulating device 7.
- FIG. 2 shows a flowchart of an advantageous program for controlling the device 1 according to the invention.
- the program starts at point 8. Under program point 9, the transmitting device 4 and the receiving device 6 are switched on. If the received signals r are below a predetermined signal level - the corresponding check is carried out at program point 11 - the program jumps to program point 17. If, on the other hand, the received signals r are above the predetermined signal level, they are stored over a certain period of time (for example several seconds). The period taken into account is usually a multiple of the period of the interrogation signal. At program point 13, the stored received signals r are divided at least approximately into k intervals of n measurement data each. So k is an integer that is less than or equal to the number of stored received signals r divided by n.
- c (n) ⁇
- n measured values are within a first k interval with the measured values of one of the subsequent k intervals are compared. hereby it can be determined whether in the considered intervals periodic signal components occur due to interference signals known or unknown origin. There different interval lengths are considered the value of n at which the difference c (n) is minimal is the period of the interference signal. This investigation leads the computing / regulating device 7 at program point 14.
- n is the number of signals received in k Interval; k is an integer that is less than that Number of signals received divided by n; i takes the Values from 1 to n-1.
- the received signals r over a Period of the interrogation signal saved.
- the interference signal a (i) is at program point 18 from the periodic Received signals r (i) subtracted. This calculation must taking into account the information, how often the n measured values within a period of the cyclic Query signal occur. This is required in order to Synchronization between the received signals that the Show period of the interrogation signal, and the periodic to achieve occurring interference signals.
- the interference signal a (i) is updated. This Update is done continuously with a Time constants that are an integer multiple f one Cycle 'of the monitor is. f controls the time constant of the signal update. To Processing of point 20 jumps the program to point 18 back and frees the received signals r (i) from the periodically occurring interference signals in which the loop, formed from the program points 18, 19 20, go through becomes.
Description
Die Erfindung betrifft eine Vorrichtung zur Überwachung eines elektronischen Sicherungselementes in einer Abfragezone, bestehend aus einer Sendeeinrichtung, die zumindest ein periodisches Abfragesignal in die Abfragezone aussendet, wobei das Abfragesignal das Sicherungselement zur Aussendung eines Erkennungssignals anregt, einer Empfangseinrichtung, die das Erkennungssignal empfängt, und einer Rechen-/Regeleinheit, die die von der Empfangseinrichtung empfangenen Signale auswertet und bei Identifizierung des Sicherungselementes einen Alarm auslöst.The invention relates to a device for monitoring of an electronic security element in one Interrogation zone, consisting of a transmission device, the at least one periodic interrogation signal in the interrogation zone sends out, the interrogation signal the security element stimulates to send a detection signal, one Receiving device which receives the detection signal, and a computing / control unit that the by the Received device evaluates signals and at Identification of the security element an alarm triggers.
Zur Detektierung von elektromagnetischen Sicherungselementen in einer Abfragezone wird in der EP 123 586 B vorgeschlagen, zusätzlich zu zwei Abfragefelder mit den Frequenzen F1 und F2 im kHz-Bereich ein Feld mit einer im Hz-Bereich liegenden Frequenz F3 in die Abfragezone zu senden. Die beiden Abfragefelder mit den Frequenzen F1 und F2 regen ein in der Abfragezone befindliches Sicherungselement zur Aussendung eines Erkennungssignals mit den Intermodulationsfrequenzen n•F1 ± m•F2 (n, m = 0, 1, 2,...) an. Das niederfrequente Abfragefeld bewirkt, daß das Sicherungselement im Takt dieses Feldes von der Sättigung in eine Richtung zur Sättigung in die andere Richtung getrieben wird. Das charakteristische Signal tritt daher periodisch mit der Frequenz des niederfrequenten Feldes auf.For the detection of electromagnetic security elements in an interrogation zone, EP 123 586 B suggested, in addition to two query fields with the Frequencies F1 and F2 in the kHz range a field with an im Hz range lying frequency F3 in the interrogation zone send. The two query fields with the frequencies F1 and F2 stimulate one in the query zone Security element for sending a detection signal with the intermodulation frequencies n • F1 ± m • F2 (n, m = 0, 1, 2, ...). The low frequency query field causes the fuse element in time with this field of the Saturation in one direction to saturation in the other Direction is driven. The characteristic signal occurs therefore periodically with the frequency of the low frequency Field.
Als alternative Lösung ist auch bekannt geworden, lediglich ein im kHz-Bereich liegendes Abfragefeld zur Erregung des Sicherungselementes zu verwenden, wobei das Erkennungssignal des Sicherungselementes wiederum im Takte eines niederfrequenten Feldes, das das weichmagnetische, nicht-lineare Material zwischen den beiden Sättigungen hin- und hertreibt, auftritt.An alternative solution has also become known, merely a query field in the kHz range to excite the Use security element, the Recognition signal of the security element in turn in time of a low-frequency field, which is the soft magnetic non-linear material between the two saturations and drives, occurs.
Desweiteren ist bereits bekannt geworden, Störquellen, die
einen Bezug zu der bekannten Frequenz der Energieversorgung
oder deren Harmonischen haben, von den empfangenen Signalen
zu entfernen, wodurch sich die Meßgenauigkeit der
Überwachungsvorrichtung erheblich erhöhen läßt. Ein
entsprechendes Verfahren wird beispielsweise in der EP 0
431 341 B1 beschrieben.
Nachteilig bei den bisher bekannt gewordenen Überwachungsvorrichtungen
ist, daß sie nur zur Beseitigung von
Störsignalen mit bekannten Frequenzen geeignet sind. Bei
zeitweise auftretenden periodischen Störsignalen, die
keinen Bezug zu der Frequenz der Energieversorgung
aufweisen, versagen sie.Furthermore, it has already become known to remove interference sources which have a relation to the known frequency of the energy supply or its harmonics from the received signals, as a result of which the measuring accuracy of the monitoring device can be increased considerably. A corresponding method is described, for example, in EP 0 431 341 B1.
A disadvantage of the monitoring devices that have become known so far is that they are only suitable for eliminating interference signals with known frequencies. In the case of intermittent periodic interference signals that have no relation to the frequency of the energy supply, they fail.
Der Erfindung liegt die Aufgabe zugrunde, eine Vorrichtung vorzuschlagen, die das Erkennen von Artikeln, die mit elektronisch detektierbaren Sicherungselementen ausgestattet sind, innerhalb einer Abfragezone verbessert.The invention has for its object a device propose the recognition of articles related to electronically detectable security elements are improved within a query zone.
Die Aufgabe wird dadurch gelöst, daß die Rechen-/Regeleinrichtung die während einer vorgegebenen Zeitspanne empfangenen Signale aufzeichnet, anhand der Signale bestimmt, ob und gegebenenfalls mit welcher Periode Störsignale auftreten und diese Störsignale von den empfangenen Signalen entfernt. Damit ermöglicht es die erfindungsgemäße Vorrichtung, neben periodisch auftretenden Störsignalen bekannter Herkunft auch periodisch auftretende Störsignale zu eliminieren, die von Störquellen mit unbekannten Interferenzfrequenzen herrühren. Als Beispiel ist die Steuerung der Energieversorgung für Registrierkassen in Supermärkten zu nennen.The object is achieved in that the computing / control device the during a given period of time received signals recorded, based on the signals determines whether and if so with which period Interference signals occur and these interference signals from the received signals removed. This enables the device according to the invention, in addition to periodically occurring Interference signals of known origin also occur periodically Eliminate interference signals from sources of interference with unknown interference frequencies. As an an example is the control of the energy supply for Cash registers in supermarkets.
Gemäß einer vorteilhaften Weiterbildung der erfindungsgemäßen Vorrichtung ist vorgesehen, daß die Rechen-/Regeleinrichtung mindestens k*n Meßwerte, wobei n = 1, 2,3, ... und k eine ganze Zahl ist, die kleiner als die Anzahl der empfangenen Signale geteilt durch n ist, während der vorgegebenen Zeitspanne tp aufzeichnet und anhand eines Vergleichs von ersten n Meßwerte mit nachfolgenden n Meßwerten ermittelt, ob innerhalb des n Meßwerte umfassenden k Intervalls periodische Störsignale auftreten.According to an advantageous development of the The device according to the invention provides that the Computing / control device at least k * n measured values, where n = 1, 2,3, ... and k is an integer smaller than that Number of signals received divided by n while the specified time period tp records and based a comparison of first n measured values with subsequent n Measured values determined whether within the n measured values comprehensive k interval periodic interference signals occur.
Als besonders günstig hat es sich erwiesen, wenn die
Rechen-/Regeleinrichtung das Auftreten von periodischen
Signalen über die Beträge der Differenzen nach folgender
Formel ermittelt:
Eine vorteilhafte Weiterbildung der erfindungsgemäßen Vorrichtung schlägt vor, daß die Rechen-/Regeleinrichtung anhand der kleinsten sich ergebenden Differenz c(n) das periodische Störsignal ermittelt, wenn die Differenz c(n) kleiner ist als ein vorgegebener maximaler Wert cmax , der einen Bruchteil des durchschnittlichen Störsignals repräsentiert.An advantageous development of the device according to the invention proposes that the computing / control device determines the periodic interference signal on the basis of the smallest resulting difference c (n) if the difference c (n) is smaller than a predetermined maximum value c max , which is a fraction represents the average interference signal.
Vorteilhafterweise bestimmt die Rechen-/Regeleinrichtung
das anfängliche durchschnittliche Störsignal a(i), über das
k Intervall von n Meßdaten nach folgender Formel:
Das derart ermittelt periodisch Störsignal wird dann von den empfangenen Signalen subtrahiert.The interfering signal thus periodically determined is then from subtracted from the received signals.
Um sicherzustellen, daß die Rechen-/Regeleinrichtung bei der erfindungsgemäßen Ermittlung von Störsignalen stets über die aktuellen Werte von periodisch auftretenden Störsignalen verfügt, werden die Meßdaten mit einer fest vorgegebenen Zeitkonstante, die ein ganzzahliges Vielfaches f der Zeitdauer eines Zyklus' des Überwachungssystems ist, aktualisiert.To ensure that the computing / control device at the determination of interference signals according to the invention always about the current values of periodically occurring Interference signals, the measurement data are fixed with a predetermined time constant, which is an integer multiple f is the duration of one cycle of the surveillance system, updated.
Die Erfindung wird anhand der nachfolgenden Figuren näher
erläutert. Es zeigt:
Fig. 1 zeigt eine schematische Darstellung der
erfindungsgemäßen Vorrichtung 1 zur Detektierung eines mit
einem Sicherungselement 2 versehenen Artikels 6 in einer
Abfragezone 3. Die Abfragezone 3 wird von zwei im
wesentlichen parallel aufgestellten Detektorgattern
gebildet, die die Sendevorrichtung 4 und die
Empfangsvorrichtung 5 enthalten. Selbstverständlich können
beide Vorrichtungen 4, 5 auch in einem Detektorgatter
untergebracht sein. Die Steuerung der Überwachungsvorrichtung
1 sowie die Auswertung der Meßwerte erfolgt
mittels der Rechen-/Regeleinrichtung 7.Fig. 1 shows a schematic representation of the
Device 1 according to the invention for detecting a
a securing
In Fig. 2 ist ein Flußdiagramm eines vorteilhaften
Programms zur Ansteuerung der erfindungsgemäßen Vorrichtung
1 dargestellt. Der Start des Programms erfolgt bei Punkt 8.
Unter Programmpunkt 9 werden die Sendevorrichtung 4 und die
Empfangsvorrichtung 6 eingeschaltet. Liegen die empfangenen
Signale r unterhalb eines vorgegebenen Signalpegels - die
entsprechende Überprüfung erfolgt bei Programmpunkt 11 -,
springt das Programm vor auf den Programmpunkt 17.
Liegen die empfangenen Signale r hingegen über dem
vorgegebenen Signalpegel, werden sie über einen gewissen
Zeitraum (z.B. mehrere Sekunden) gespeichert. Üblicherweise
ist der berücksichtigte Zeitraum ein Vielfaches der Periode
des Abfragesignals.
Bei Programmpunkt 13 werden die gespeicherten empfangenen
Signale r zumindest näherungsweise in k Intervalle von
jeweils n Meßdaten unterteilt. k ist also eine ganze Zahl,
die kleiner als die Anzahl oder gleich der Anzahl der
gespeicherten empfangenen Signale r geteilt durch n ist.
Dann werden die n Meßwerte der einzelnen k Gruppen nach
folgender Formel miteinander verglichen:
If, on the other hand, the received signals r are above the predetermined signal level, they are stored over a certain period of time (for example several seconds). The period taken into account is usually a multiple of the period of the interrogation signal.
At
Im Klartext bedeutet dies, daß die n Meßwerte innerhalb
eines ersten k Intervalls mit den Meßwerten eines der
nachfolgenden k Intervalle verglichen werden. Hierdurch
läßt sich ermitteln, ob in den betrachteten Intervallen
periodische Signalanteile auftreten, die auf Störsignale
bekannter oder unbekannter Herkunft zurückzuführen sind. Da
unterschiedliche Intervallängen betrachtet werden, liefert
derjenige Wert von n, bei dem die Differenz c(n) minimal
ist, die Periode des Störsignals. Diese Untersuchung führt
die Rechen-/Regeleinrichtung 7 bei Programmpunkt 14 aus.In plain text this means that the n measured values are within
a first k interval with the measured values of one of the
subsequent k intervals are compared. hereby
it can be determined whether in the considered intervals
periodic signal components occur due to interference signals
known or unknown origin. There
different interval lengths are considered
the value of n at which the difference c (n) is minimal
is the period of the interference signal. This investigation leads
the computing / regulating
Unter Programmpunkt 15 wird überprüft, ob die Differenz
c(n) unterhalb eines vorgegebenen Wertes liegt, der einem
vorgegebenen Bruchteil des durchschnittlichen Störsignals
entspricht. Wird die Frage verneint, springt das Programm
auf Punkt 17. Liegt die Differenz c(n) hingegen unterhalb
des vorgegebenen Wertes, wird unter Programmpunkt 16 ein
durchschnittliche Störsignal a(i) ermittelt. Die Berechnung
erfolgt nach folgender Formel:
Hierbei ist n die Anzahl der empfangenen Signale in einem k Intervall; k ist eine ganze Zahl, die kleiner ist als die Anzahl der empfangenen Signale geteilt durch n; i nimmt die Werte von 1 bis n-1 an.Here n is the number of signals received in k Interval; k is an integer that is less than that Number of signals received divided by n; i takes the Values from 1 to n-1.
Bei Punkt 17 werden die empfangenen Signale r über eine
Periode des Abfragesignals gespeichert. Das Störsignal a(i)
wird bei Programmpunkt 18 von den periodischen
Empfangssignalen r(i) subtrahiert. Diese Berechnung muß
unter Berücksichtigung der Information erfolgen, wie oft
die n Meßwerte innerhalb einer Periode des zyklischen
Abfragesignals auftreten. Erforderlich ist dies, um eine
Synchronisation zwischen den empfangenen Signalen, die die
Periode des Abfragesignals zeigen, und den periodisch
auftretenden Störsignalen zu erzielen.At
Unter Punkt 20 wird das Störsignal a(i) aktualisiert. Diese Aktualisierung erfolgt kontinuierlich mit einer Zeitkonstanten, die ein ganzzahliges Vielfaches f eines Zyklus' der Überwachungsvorrichtung ist. f steuert somit die Zeitkonstante der Signalaktualisierung. Nach Abarbeitung des Punktes 20 springt das Programm auf Punkt 18 zurück und befreit die empfangenen Signale r(i) von den periodisch auftretenden Störsignalen, in dem die Schleife, gebildet aus den Programmpunkten 18, 19 20, durchlaufen wird. Under point 20, the interference signal a (i) is updated. This Update is done continuously with a Time constants that are an integer multiple f one Cycle 'of the monitor is. f controls the time constant of the signal update. To Processing of point 20 jumps the program to point 18 back and frees the received signals r (i) from the periodically occurring interference signals in which the loop, formed from the program points 18, 19 20, go through becomes.
- 11
- Überwachungsvorrichtungmonitoring device
- 22
- Sicherungselementfuse element
- 33
- Abfragezoneinterrogation zone
- 44
- Sendevorrichtungtransmitting device
- 55
- Empfangsvorrichtungreceiving device
- 66
- Artikelitems
- 77
- Rechen-/RegeleinrichtungComputing / control unit
Claims (7)
- An apparatus (1) for the surveillance of an electronic security element (2) in an interrogation zone (3), comprising a transmit device (4) emitting at least one cyclic interrogation signal into the interrogation zone (3), said interrogation signal causing the security element to deliver a characteristic signal, a receive device (5) receiving the characteristic signal, and a computing/control unit (7) evaluating the signals (r(i)) received from the receive device and releasing an alarm when the presence of the security element is established,
characterized in that the computing/control unit (7) records the signals (r(i)) received during a predetermined time period (tp),
that it determines from the received signals (r) whether and at what cycle, if applicable, interference signals (a(i)) occur in the received signals (r(i)),
and that it removes the detected interference signals (a(i)) from the received signals (r(i)). - The apparatus as claimed in claim 1,
characterized in that the computing/control unit (7) records during the predetermined time period tp at least k*n measured values, where n = 1, 2, 3 ...z, and k is an integer number smaller than the number of received signals (r) divided by n, and determines from a comparison of the n measured values of a first k interval with the n measured values of succeeding k intervals whether cyclic interference signals (a(i)) occur within the time period encompassing n measured values. - The apparatus as claimed in claim 2,
characterized in that the computing/control unit (7) determines the differences (c(n)) for different numbers of n measured values in k intervals by applying the following formula: - The apparatus as claimed in claim 2 or 3,
characterized in that the computing/control unit (7) determines the cyclic interference signal from the lowest resulting difference cmin(n) when said difference cmin (n) lies below a predetermined maximum value cmax(n). - The apparatus as claimed in claim 4,
characterized in that the computing/control unit (7) calculates an initial averaged interference signal (a(i)) over the interval of n measured values using the following formula: - The apparatus as claimed in claim 5,
characterized in that the computing/control unit (7) subtracts the averaged cyclically occurring interference signal (a(i)) from the received signals (r(i)). - The apparatus as claimed in one or several of the preceding claims,
characterized in that the computing/control unit (7) performs an update on the determination of interference signals (a(i)) with a fixed predetermined time constant.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19644927 | 1996-10-29 | ||
| DE19644927A DE19644927A1 (en) | 1996-10-29 | 1996-10-29 | Device for monitoring an electronic security element in an interrogation zone |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0840266A1 EP0840266A1 (en) | 1998-05-06 |
| EP0840266B1 true EP0840266B1 (en) | 2002-01-16 |
Family
ID=7810307
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP97117103A Expired - Lifetime EP0840266B1 (en) | 1996-10-29 | 1997-10-02 | Device for monitoring a security element in an interrogation area |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US5894270A (en) |
| EP (1) | EP0840266B1 (en) |
| DE (2) | DE19644927A1 (en) |
| ES (1) | ES2171800T3 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6750768B2 (en) * | 2002-04-15 | 2004-06-15 | Wg Security Products, Inc. | EAS system employing pseudorandom coding system and method |
| US6753821B2 (en) * | 2002-04-22 | 2004-06-22 | Wg Security Products, Inc. | Method and arrangement of antenna system of EAS |
| US8131239B1 (en) | 2006-08-21 | 2012-03-06 | Vadum, Inc. | Method and apparatus for remote detection of radio-frequency devices |
Family Cites Families (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4168496A (en) * | 1977-10-05 | 1979-09-18 | Lichtblau G J | Quasi-stationary noise cancellation system |
| US4459474A (en) * | 1981-05-18 | 1984-07-10 | Walton Charles A | Identification system with separation and direction capability and improved noise rejection |
| US4668942A (en) * | 1984-11-19 | 1987-05-26 | Progressive Dynamics, Inc. | Signal analysis apparatus including recursive filter for electromagnetic surveillance system |
| US4630035A (en) * | 1985-01-04 | 1986-12-16 | Motorola, Inc. | Alarm system having alarm transmitter indentification codes and acoustic ranging |
| US4679035A (en) * | 1985-07-30 | 1987-07-07 | Sensormatic Electronics Corporation | Tri-signal electromagnetic article surveillance system |
| US4975681A (en) * | 1989-12-07 | 1990-12-04 | Sensormatic Electronics Corporation | Interfering signal rejection circuitry and electronic article surveillance system and method employing same |
| US5023598A (en) * | 1990-01-02 | 1991-06-11 | Pitney Bowes Inc. | Digital signal processor for electronic article gates |
| GB9009739D0 (en) * | 1990-05-01 | 1990-06-20 | Disys Inc | Transponder system |
| US5300922A (en) * | 1990-05-29 | 1994-04-05 | Sensormatic Electronics Corporation | Swept frequency electronic article surveillance system having enhanced facility for tag signal detection |
| SE9203479L (en) * | 1992-01-20 | 1993-07-21 | Rso Corp | SET UP AND DEVICE FOR ELECTRONIC IDENTIFICATION |
| US5349339A (en) * | 1992-04-07 | 1994-09-20 | Actron Entwicklungs Ag | Apparatus for the detection of labels employing subtraction of background signals |
| US5495229A (en) * | 1994-09-28 | 1996-02-27 | Sensormatic Electronics Corporation | Pulsed electronic article surveillance device employing expert system techniques for dynamic optimization |
| US5673024A (en) * | 1996-04-22 | 1997-09-30 | Sensormatic Electronics Corporation | Electronic article surveillance system with comb filtering by polyphase decomposition and nonlinear filtering of subsequences |
| US5699045A (en) * | 1996-06-06 | 1997-12-16 | Sensormatic Electronics Corporation | Electronic article surveillance system with cancellation of interference signals |
-
1996
- 1996-10-29 DE DE19644927A patent/DE19644927A1/en not_active Withdrawn
-
1997
- 1997-09-30 US US08/941,286 patent/US5894270A/en not_active Expired - Fee Related
- 1997-10-02 EP EP97117103A patent/EP0840266B1/en not_active Expired - Lifetime
- 1997-10-02 ES ES97117103T patent/ES2171800T3/en not_active Expired - Lifetime
- 1997-10-02 DE DE59706000T patent/DE59706000D1/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| DE19644927A1 (en) | 1998-04-30 |
| DE59706000D1 (en) | 2002-02-21 |
| EP0840266A1 (en) | 1998-05-06 |
| US5894270A (en) | 1999-04-13 |
| ES2171800T3 (en) | 2002-09-16 |
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