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Publication numberUS3859652 A
Publication typeGrant
Publication dateJan 7, 1975
Filing dateJun 26, 1972
Priority dateJun 26, 1972
Publication numberUS 3859652 A, US 3859652A, US-A-3859652, US3859652 A, US3859652A
InventorsKenneth Clarkson, Roger L Hall, Edward S Wainwright
Original AssigneeNorth American Systems Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method and apparatus for detecting the theft of articles
US 3859652 A
Abstract
The theft of articles or goods maintained in a vending place such as a department store having at least one exit passageway is prevented by affixing thereto a preferably small detection element comprising a receiver of first predetermined frequency, a transmitter of second predetermined frequency, and power supply means coupled from said receiver and capable of disabling said transmitter. At the authorized checkout area of the store there is disposed a relatively high power transmitter of first predetermined frequency capable of preferably permanently disabling the power supply means and in turn said transmitter of second predetermined frequency of the detection element. In one preferred embodiment the power supply means includes a rectifier circuit which is destroyed (burned out and thus opened) when the detection element comes within predetermined proximity to the high power transmitter at the checkout area. At the exitway there is disposed a transmitter of first predetermined frequency and a receiver of second predetermined frequency which only detects a signal when the power supply means has not been disabled at the authorized checkout area whereby an alarm signal is generated.
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United States Patent 1191 Hall et al. Jan. 7, 1975 [5 METHOD AND APPARATUS FOR 3,711,848 1 1973 Martens 340/280 DETECTING THE THEFT 05* ARTICLES 3,713,133 1/1973 Nathans.... 340/224 X 3,720,940 3/1973 Fox 340/280 X [75] Inventors: Roger L. Hall, Francestown;

Edward famwnght, Nashua 1 Primary Examiner-Glen R. Swann, Ill 22 f Clarkson, Attorney, Agent, or Firm-Wolf, Greenfield & Sacks nas e, as

[73] Assignee: North American Systems Corp., [57] ABSTRACT f 'l by Sam Hall The theft of articles or goods maintained in a vending and wamwl'lght place such as a department store having at least one [22] Filed; Inez/5,1972 exit passageway is prevented by affixingthereto a preferably small detection element comprising a re- 1 PP N0: 266,130 ceiver of first predetermined frequency, a transmitter of second predetermined frequency, and power supply 52 us. CI 340/280, 340/224, 343/6.8 R w cqupled m Said receiver and m 511 1m. 01. G08b 13/22 ablmg Said transmllter- A E authomeicheckgtut 58 Field of Search 340/258 R, 280, 224; area of the Store there IS deposed a relatively hlgh 325/16, 21 135, 343/63 R power transmitter of first predeternrmed frequency capable of preferably permanently disabling the power v 5 References Cited supply means and in turn said transmitter of second UNITED STATES PATENTS predetermined frequency of the detection element. In one preferred embodiment the power supply means 2,241,283 7/l358 l-lallden 325/l85 UX includes a rectifier circuit which is destroyed (burned 1 331 y fig out and thus opened) when the detection element 3088l06 4/1963 i comes within predetermined proximity to the high H1967 'ix'j power transmitter at the checkout area. At the exit- 3,418,655 12/1968 Baylor way there is disposed a transmitter of first predeter- 3,493,955 2/1970 Minasy mined frequency and a receiver of second predeter- 3,546,695 12/1970 Freedman.... 343/6.8 X mined frequency which only detects a signal when the 3,582,931 6/1971 Nawrocki 340/280 X power supply means has not been disabled at the auf g l thorized checkout area whereby an alarm signal is c inc cy 3,685,050 '8/1972 Cartwright... 343/6.8 x generated 3,707,711 12/1972 Cole 340/280 6 Claims, 7 Drawing Figures FRFNEMIFEFTEI I I I I 24 I 1 I J I C3 I g 02/5 I IL I 11.2 Y I 36 I I 0 1 I I L M F 7 J 1 1 SZ 4. c1 1.1; I I l I L E EDEE 3L 1 Patented Jan. 7, 1975 2 Sheets-Sheet 2 TRZRISTAITTEFTE I l l I l g I I C3 g 02;; IL .L2 5 ix Y I 2 l I I L .E I

MODULATOR T a V V y REcEIvER POWER I- TRANSMITTER RI SUPPLY f T2 TRANSMWTER ARTICLE RECEIVER DEMODULATOR ACCUMULATOR TI R2 4 2 iifF/a' 5 METHOD AND APPARATUS FOR DETECTING THE THEFT OF ARTICLES FIELD OF THE INVENTION The present invention relates in general to an apparatus or system and associated method of detecting the theft of articles from a vending place such as a department store. More particularly, the present invention is directed to the type of system that employs an electronic detection element preferably of small integratedcircuit size affixed to the article or goods.

BACKGROUND OF THE INVENTION Many different means have been devised for preventing or deterring the theft of articles or goods from a store or other vending place. Some of these means include mirrors, security police, cameras, television with video recording and gentian violet marking. None of these means are completely effective, and once the thief has been able to conceal the item these above devices cannot detect the passage of the item through the exitway of the store.

The problem of stolen merchanidse is further complicated by the possible legal rights of the individual against false accusations. Thus, persons in authority at the store are hesitant to accuse any potential thief,'in the absence of effective detection means, for fear of the possibility of a suit for defamation of character being filed. Also, any false accusations may have a deleterious outcome regarding the good-will of the store.

Accordingly, it is important that the detection means accurately identify, preferably at the exitway of the store, articles that have not passed through the checkout counter and been paid for. In the past there have been both electrical and mechanical devices designed. Generally, however, these devices are too costly, too dangerous, or too unreliable. One technique, for example, shown in U.S. Pat. No. 3,582,931 uses a radioactive material affixed to the article. The problem with this technique is that the articles carrying the material may be adversely affected by the presence of any radioactive material. Another technique is to use a sensitive reed switch (see US. Pat. No. 3,577,136 which is responsive to a magnet disposed at the exitway. This type of adevice has, inter alia, the disadvantage that it can be too easily falsely triggered. Still another prior art device is of the resonant frequency type (see U.S. Pat. Nos. 3,493,955 and 3,500,373) wherein a resonant circuit is affixed to the article and a receiver/transmitter combination. is used to monitor changes in the ambient energy level due to the presence of the resonant circuit. This device also is susceptible to false triggering because the frequency sensitivity of the energy level monitoring equipment is quite low and metal objects can cause false triggering.

OBJECTS OF THE INVENTION Accordingly, it is an important object of the present invention to provide an improved apparatus or system and associated method for detecting the theft or articles or goods from a vending place such as a department store. The apparatus of the present invention is of the electromagnetic wave detection type.

Another object of the present invention is to provide a system for preventing article thefts that is both safe and effective in operation. With the apparatus of the present invention there is no exposure to harmful radiation.

A further object of the present invention is to provide an apparatus for monitoring the unauthorized passage of articles'past a predetermined checkpoint preferably adjacent an exitway of the store wherein there is no need for additional security personnel and wherein the apparatus is readily concealable from the view of the ordinary purchaser.

Still another object of the present invention is to provide a system for preventing article thefts that effectively distinguishes between the authorized and unauthorized passage of articles past a given checkpoint thereby alleviating the false alarm problem.

An additional object of the present invention is to provide a detection element that readily impregnates or adheres to various articles whether constructed of paper, cloth, wood, plastic, etc. that is very small in size, and that may be easily disabled [by even non-skilled workers.

SUMMARY OF THE INVENTION To accomplish the foregoing and other objects of the invention, there is provided a system for detecting the unauthorized removal of articles from an enclosure such as a department store having a checkout area and a passageway through which the articles are generally moved from the enclosure. The system comprises a transmitter of a first frequency and] a receiver of a second frequency both being disposed at the exit passageway. The receiver of second frequency is not responsive to a signal of first frequency. A means is also provided for establishing an alarm condition when the receiver at the passageway receives a signal of second frequency.

A relatively small detection element is attached to the article and comprises a receiver of first frequency, a transmitter of second frequency and means responsive to a signal, of a level less than a predetermined threshold level, from said receiver of a first frequency for providing power to the transmitter of a signal of second frequency.

If the article'is properly taken from the enclosure it passes through a checkout area where there is located a high power transmitter of a first frequency for estab lishing a signal of a level greater than the predetermined threshold level from the receiver of the detection element to thereby disable the power providing means, interrupting power to the transmitter of the detection element. Thereafter, when the detection element passes through the exit passageway the receiver of second frequency disposed at the exit passageway does not receive a signal because of the permanently disabled power providing means and therefore no alarm cpndition is established. Alternatively, if the article does not pass as it should through the checkout counter area and is not subjected to the high power transmitter disposed thereat, the means for providing power to the transmitter of the detection element is not inhibited and thus as the article passes through the exit passageway the receiver disposed at the passageway will receive a signal of a second frequency and thus there will be an alarm condition established.

In accordance with another aspect of the present invention the transmitter of a second frequencywhich forms part of the detection element has a modulation means associated therewith. Each of the modulation means is different for each type of article being protected. By using a first frequency transmitter and second frequency receiver just before the checkout area, it is possible to keep track of all articles passing to the checkout area for purposes of inventory control. For this purpose it is also necessary to have some type of accumulator for distinguishing each article and providing a cumulative count of each article sold.

BRIEF DESCRIPTION OF THE DRAWINGS Numerous other objects, features and advantages of the invention should now become apparent upon a reading of. the followingdetailed description taken in t conjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram showing the different areas of the store and the components of the present invention associated therewith;

FIG. 2A shows a block diagram of the detection element of the present invention;

FIG. 2B shows a block diagram of the means provided at the checkout area of the store;

FIG. 2C is a block diagram of the means provided at the exitway area of the store;

FIG. 3 is a circuit diagram of a preferred embodiment of the detection element shown in FIG. 2A;

FIG. 4 shows a block diagram of an alternate embodiment for the detection element; and

FIG. 5 is a block diagram of the inventory monitoring means of the present invention used in conjunction with the detection element of FIG. 4.

DETAILED DESCRIPTION FIG. 1 shows the three basic areas of a store that are of interest in discussing the concepts of the present invention. Various articles are disposed in storage or display area in any known manner and preferably each article A has a detection element affixed thereto. FIG. 2A which is discussed in more detail hereinafter shows a block diagram of one detection element of this invention. If the article is being properly purchased it passes from area 10 to checkout area 12 where there is usually disposed a checkout counter '14 and associated cash register 16 or the like. The high power transmitter of the present invention is disposed at the checkout area 12 for disabling the detection element and permitting passage of the article through the exitway area 14 without providing an alarm. This high power transmitter may be disposed beneath the recess 18 provided in counter-top 20 of checkout counter 14. A pair of doors 21 is shown in FIG. 1 for providing final access to the outside of store or enclosure 22.

If the article A has not passed through the checkout area 12 and has not been subjected to the high power transmitter thereat, when the article does pass through the doors 21 means are provided adjacent thereto as discussed with reference to FIG. 2C for providing an alarm.

Referring now to FIG. 2A there is shown a block diagram of the detection element 24 which is affixed to article A in an appropriate manner. This detection element 24 is preferably constructed by integrated circuit technology and may be no larger than 0.025 sq. in. The detection element 24 includes an input antenna 26 which couples to receiver R1. Receiver R1 is preferably a fixed frequency receiver of frequency Fl which may be on the order of 460 megacycles. The detection element 24 also includes a transmitter T2 (and associated antenna 27), and a power supply 30 coupled from receiver R1 for delivering power to both receiver R1 and transmitter T2 when an input signal of frequency F1 is received on antenna 26. Transmitter T2 may be of conventional design. Power supply 30 which is discussed later with reference to FIG. 3 preferably includes a rectifier that is preselected so that if a power greater than a predetermined threshold is received by receiver R1 the rectifier of the power supply 30 is burned out (opened) and thus when any future signal is received by receiver R1 the power supply 30 blocks power to transmitter T2 and prevents any transmission of its associated frequency FZ. Frequency F2 may be on the order of 430 megacycles.

FIG. 2B shows the checkout area 12 and the transmitter 32 which is a high power transmitter capable of generating sufficient energy when the article is passed over the transmitter to cause the rectifier of power supply 30 to be opened.

In FIG. 2C there is shown the exitway area 14 including a transmitter T1 (with associated antenna 28) of first frequency F1 and a receiver R2 (with associated antenna 29) of second frequency F2 having an alarm 34 associated therewith for generating an alarm signal when a signal of frequency F2 is received by receiver R2. If the article has been appropriately passed through checkout area 12 and passes as shown in FIG. 2C between transmitter T1 and receiver R2 the signal from transmitter T1 is blocked because the rectifier of power supply 30 has prevented transmission of any F2 frequency, and thus receiver R2 does not trigger alarm 34.

Referring now to FIG. 3, there is shown a circuit diagram for one embodiment of the detection element 24 shown in a block diagram in FIG. 2A. The detection element 24 comprises a receiver R1, a transmitter T2, and power supply 30. The receiver R1 includes a tank circuit comprised of capacitor C1 and an inductor L1. Similarly, transmitter T2 includes a tank circuit comprised of capacitor C2 and inductor L2. The inductors of these tank circuits function as the antennas of each tank circuit.

The power supply means 30 comprises transistor Q1, diode D1, capacitors C3 and C4 and ressistor R. The collector of transistor Q1 couples to transmitter T2 and the emitter of transistor Q1 couples by way of a diode D1 to receiver R1. Capacitor C3 also couples from the emitter of transistor 01 to both receiver R1 and transmitter T2. Resistor R and capacitor C4 are coupled, in parallel, from the base of transistor O1 to transmitter T2. Resistor R establishes the proper bias for the base of transistor 01 and capacitor C4 is an AC bypass capacitor. It is the diode D1 that is destroyed when receiver Rl receives a signal of strength greater than a predetermined threshold level. This level is a function of the type diode selected. When diode D1 is burned out transistor Q1 can no longer supply power to either receiver R1 or transmitter T2.

Because the receiving and transmitting antennas (inductors L1 and L2, respectively) are much smaller than a half wave, an optimum inpedance match has been calculated at the terminals of the antenna, of approximately 73 ohms. By chosing a five microfarad capacitor for capacitor C1 and assuming a resonant frequency of 460 MHZ for receiver R1, an inductance of approximately 6,000 y. henries can be calculated for inductor L1. A loop of wire whose radius is 1/50 inch and whose thickness is 4 X l0" inch can be used for inductor L.

Using the same value of capacitance for capacitor C2 the inductance in the transmitter can be calculated to be approximately 5,800 up. henries, assuming that the transmitter T2 has a resonant frequency on the order of 430 MHZ.

Thus, when the receiver R1 is receiving a signal of frequency F1, diode D1 rectifies the output from the tank circuit of receiver R1 andtransistor Q1 provides power by way of capacitor C3 to both receiver R1 and transmitter T2. A feedback line 36 couples from transmitter T2 to capacitor C4 for providing regenerative feedback to the power supply means 30. When the circuit shown in FIG. 3 is passed adjacent the transmitter 32 shown in FIG. 2, the power from the transmitter 32 which is received by receiver R1 is sufficient to burn out diode D1, thereby inhibiting the power supply means 30 and the transmitter T2 shown in FIG. 3. When the article is subsequently passed through the exitway area 14 shown in FIG. 2C the transmitter T2 is not capable of sending any signal to receiver R2 at the exitway area and thus no alarm condition is generated. If the circuit of FIG. 3 is not subjected to the high power transmitter 32 the diode D1 is not burned out and thus transmitter T2 is capable of generating a signal received by receiver R2 at the exitway area 14 for generating an alarm condition by means of alarm 34.

Referring now to FIG. 4 there is shown a block diagram of another embodiment of a detection element of 24. The block diagram of FIG. 4 is similar to the previous block diagram of FIG. 2A with the addition of a modulator 40 which receives an input from power supply 30 and has an output connected to transmitter T2. Modulator 40 may be of conventional design. When receiver R1 receives a signal of frequency F1, power supply 30 provides power to receiver R1, transmitter T2 and modulator 40, and the output signal from the antenna associated with transmitter T2 is a modulated frequency signal. A-known type of amplitude modulation can be provided by modulator 40. With the use of the detection element of'FIG. 4 the exitway detection circuitry may be similar to that shown in FIG. 2C with the addition of a demodulator associated with receiver R2.

FIG. 5 shows a block diagram of an inventory monitoring means which may be disposed before or after the checkout area 12 (see FIG. 1). The inventory monitoring means may be used in conjunction with the high power transmitter 32 at the checkout area 12. The purpose of this inventory control means is to provide a running total of the number of total articles of each type that have been passed through the checkout area 12. By determining the total amount sold the total inventory on hand can be easily calculated.

The block diagram of FIG. 5 is similar to the one shown in FIG. 2C and comprises a tranmitter T1, a rece iver'R2, a demodulator 42, and an accumulator 44. As the article A passes between the transmitter T1 and receiver R2, a modulated signal from transmitter T2 of the detection element shown in FIG. 4 is coupled to receiver R2. The demodulator 42 demodulates this signal, thereby in effect identifying the particular article being sold, and an accumulator 44 provides a total of the particular article that has been sold over a part predetermined time period. The modulator 42 and accumulator 44 may both be of conventional design and would include various electronics components. Accumulator 44 may even be a general purpose digital computer. Also, the apparatus shown in FIG. 5 may replace the detection circuitry of FIG. 2C in one particular system.

In accordance with another aspect of this invention the transmitter Tl may have a modulator associated therewith (see FIG. 2C), in which case receiver R1 would have a demodulator associated therewith for enabling operation of power supply 30 (see FIG. 2A).

Having described some embodiments of the present invention, it should now become obvious that there are numerous other embodiments and modifications thereof all of which should fall within the spirit and scope of the present invention as defined by the appended claims.

What is claimed is:

l. A system for detecting the unauthorized removal of articles from an enclosure having a checkout area and a passageway through which said articles may be moved, said system comprising;

a transmitter of a signal of first signal characteristic disposed at said passageway,

a receiver of a signal of second signal characteristic disposed at said passageway and being nonresponsive to a signal of first signal characteristic,

means for establishing an alarm condition when said receiver receives a signal of second signal characteristic,

a detection signal attached to the article and comprising a receiver of a signal of first signal characteristic, a transmitter of a signal of second signal characteristic, and means responsive to a signal, of a level less than a predetermined threshold level, from said receiver of a signal of first signal characteristic for providing power to said transmitter of a signal of second signal characteristic,

a power transmitter of a signal of first signal characteristic disposed at said checkout area for establishing a signal of a level greater than said predetermined threshold level from said receiver of a signal of first signal characteristic to thereby inhibit the providing of power to said transmitter of a signal of second signal characteristic when said article is at said checkout area,

whereby said receiver of a signal of second signal characteristic receives a signal to thereby establish an alarm condition when an unauthorized removal of said article has occurred, and does not receive a signal when an authorized removal has occurred,

said receiver of first characteristic comprising a tank circuit and said transmitter of said second characteristic comprising a tank circuit, said power providing means including a transistor having an input electrode and an output electrode,

means for biasing the transistor including a resistor coupled to the' input electrode of the transistor, a diode coupling from the output electrode of the transistor to one of the tank circuits and capacitance means coupling from the output electrode of the transistor to both tank circuits,

each said tank circuit including an inductor defining part of the tank circuit and forming an antenna means for transmitting or receiving signals.

2. The system of claim 1 comprising a demodulator 5 associated with said receiver of a signal of second signal characteristic.

3. The system of claim 2 comprising means positioned adjacent the checkout area for registering a total count of each article passing through the checkout 6. The system of claim 1 wherein said detection eleareament comprises a modulator coupling to said transmit- 4. The system of claim 3 wherein said means for registering includes an accumulator means.

5. The system of claim 1 wherein the anode of said 5 diode couples to the output electrode and the cathode provldmg means of Sald dfitectlon elementof said diode connects to the receiver tank circuit.

ter ofa signal of second signal characteristic and means for coupling power to said modulator from said power

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2841700 *Apr 4, 1957Jul 1, 1958Hazeltine Research IncRemote-control apparatus
US2851592 *Dec 3, 1952Sep 9, 1958Rca CorpCarrier wave powered radio transceiver circuits
US2999926 *Dec 30, 1953Sep 12, 1961Rca CorpSemi-conductor signal transmitting systems
US3088106 *Apr 4, 1960Apr 30, 1963Gen Precision IncResponder device
US3307168 *Nov 19, 1962Feb 28, 1967Gen Precision IncSignalling system
US3418655 *Sep 12, 1966Dec 24, 1968Cubic CorpPseudo-coherent range rate system
US3493955 *Apr 17, 1968Feb 3, 1970Monere CorpMethod and apparatus for detecting the unauthorized movement of articles
US3546695 *Mar 3, 1969Dec 8, 1970Raytheon CoRadar transpondor system
US3582931 *Oct 18, 1967Jun 1, 1971Daniel NawrockiPilferage-prevention system
US3624631 *Apr 27, 1970Nov 30, 1971Sanders Associates IncPilferage control system
US3665448 *Aug 3, 1970May 23, 1972Hugh A McglincheyElectronic shoplifting prevention system
US3685050 *Apr 13, 1970Aug 15, 1972Cartwright Eng IncSingle antenna signal retransmission device
US3707711 *Apr 2, 1970Dec 26, 1972Peter Harold ColeElectronic surveillance system
US3711848 *Feb 10, 1971Jan 16, 1973I D Eng IncMethod of and apparatus for the detection of stolen articles
US3713133 *Feb 16, 1971Jan 23, 1973R NathansRf and sonic systems for preventing shoplifting of goods and unauthorized removal of capsules affixed thereto for protecting goods
US3720940 *Sep 29, 1970Mar 13, 1973Fox HMethod and apparatus for sorting packages and the like
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4481428 *May 19, 1981Nov 6, 1984Security Tag Systems, Inc.Batteryless, portable, frequency divider useful as a transponder of electromagnetic radiation
US4551712 *May 14, 1982Nov 5, 1985N.V. Nederlandsche Apparatenfabriek NedapElectronic detection system for detecting a responder including a frequency divider
US4642640 *Apr 25, 1983Feb 10, 1987Sensormatic Electronics CorporationSignal receptor-reradiator and surveillance tag using the same
US4724427 *Jul 18, 1986Feb 9, 1988B. I. IncorporatedTransponder device
US4818973 *Jul 14, 1987Apr 4, 1989Kabushiki Kaisha Wako SangyoSystem for detecting a transfer of an article
US5323150 *Jun 11, 1992Jun 21, 1994Micron Technology, Inc.Method for reducing conductive and convective heat loss from the battery in an RFID tag or other battery-powered devices
US5447779 *Jan 27, 1993Sep 5, 1995Tokai Electronics Co., Ltd.Resonant tag and method of manufacturing the same
US5448242 *Apr 26, 1994Sep 5, 1995Texas Instruments IncorporatedModulation field detection, method and structure
US5450087 *Apr 6, 1994Sep 12, 1995Texas Instruments IncorporatedTransponder maintenance mode method
US5471212 *Apr 26, 1994Nov 28, 1995Texas Instruments IncorporatedMulti-stage transponder wake-up, method and structure
US5572226 *Apr 11, 1995Nov 5, 1996Micron Technology, Inc.Spherical antenna pattern(s) from antenna(s) arranged in a two-dimensional plane for use in RFID tags and labels
US5589251 *Aug 22, 1995Dec 31, 1996Tokai Electronics Co., Ltd.Resonant tag and method of manufacturing the same
US5589820 *Oct 11, 1995Dec 31, 1996Pac/Scan, Inc.Retail theft prevention and information device
US5682814 *Aug 22, 1995Nov 4, 1997Tokai Electronics Co., Ltd.Apparatus for manufacturing resonant tag
US5695860 *Sep 1, 1995Dec 9, 1997Tokai Electronics Co., Ltd.Resonant tag and method of manufacturing the same
US5701121 *Dec 12, 1994Dec 23, 1997Uniscan Ltd.Transducer and interrogator device
US5864301 *May 13, 1996Jan 26, 1999Jackson; Jerome D.For receiving an interrogation signal/transmitting a circuit signal
US5990791 *Oct 22, 1997Nov 23, 1999William B. SpargurAnti-theft detection system
US6714121 *Aug 9, 1999Mar 30, 2004Micron Technology, Inc.RFID material tracking method and apparatus
US6956538Aug 28, 2002Oct 18, 2005Micron Technology, Inc.RFID material tracking method and apparatus
US7042358Aug 28, 2002May 9, 2006Micron Technology, Inc.RFID material tracking method and apparatus
US7053775Aug 28, 2002May 30, 2006Micron Technology, Inc.RFID material tracking method and apparatus
US7164380 *Aug 31, 2001Jan 16, 2007Hitachi, Ltd.Interrogator and goods management system adopting the same
US7808367 *Aug 28, 2002Oct 5, 2010Round Rock Research, LlcRFID material tracking method and apparatus
US7825867Apr 26, 2007Nov 2, 2010Round Rock Research, LlcMethods and systems of changing antenna polarization
US7932867Oct 18, 2010Apr 26, 2011Round Rock Research, LlcMethods and systems of changing antenna polarization
US7936268Aug 31, 2007May 3, 2011Round Rock Research, LlcSelectively coupling to feed points of an antenna system
US8115637Jun 3, 2008Feb 14, 2012Micron Technology, Inc.Systems and methods to selectively connect antennas to receive and backscatter radio frequency signals
US8125316Aug 28, 2002Feb 28, 2012Round Rock Research, LlcRFID material tracking method and apparatus
US8269605Aug 31, 2007Sep 18, 2012Round Rock Research, LlcRFID material tracking method and apparatus
US8378789Aug 31, 2007Feb 19, 2013Round Rock Research, LlcRFID material tracking method and apparatus
US8405509Nov 21, 2011Mar 26, 2013Micron Technology, Inc.Systems and methods to selectively connect antennas to receive and backscatter radio frequency signals
USRE35765 *Jun 21, 1996Apr 7, 1998Micron Communications, Inc.Method for reducing conductive and convective heat loss from the battery in an RFID tag or other battery-powered devices
USRE36109 *Jul 12, 1995Feb 23, 1999Kipp; LudwigCheckout system
EP0066403A1 *May 17, 1982Dec 8, 1982Automated Security (Holdings) PLCBatteryless, portable, frequency divider
EP0524081A1 *Jul 15, 1992Jan 20, 1993Commissariat A L'energie AtomiqueCommunication system between a emitter/receiver interrogator device and an emitter/receiver responder device
WO1984004987A1 *Jun 7, 1984Dec 20, 1984Patrick AbrassartTag intended to be associated to a product or article to enable to check for its presence
WO1987004282A1 *Dec 17, 1986Jul 16, 1987Advanced Systems ResearchInventory control system
Classifications
U.S. Classification340/572.3, 342/42
International ClassificationG08B13/24
Cooperative ClassificationG08B13/2414, G08B13/2434
European ClassificationG08B13/24B1G, G08B13/24B3H