DK258082A - Theft frequency detector with two frequencies - Google Patents

Theft frequency detector with two frequencies Download PDF

Info

Publication number
DK258082A
DK258082A DK258082A DK258082A DK258082A DK 258082 A DK258082 A DK 258082A DK 258082 A DK258082 A DK 258082A DK 258082 A DK258082 A DK 258082A DK 258082 A DK258082 A DK 258082A
Authority
DK
Denmark
Prior art keywords
frequencies
frequency
antenna
strips
diode
Prior art date
Application number
DK258082A
Other languages
Danish (da)
Other versions
DK161172B (en
DK161172C (en
Inventor
H B Williams
Original Assignee
Deterrent Tech Corp
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
Application filed by Deterrent Tech Corp filed Critical Deterrent Tech Corp
Publication of DK258082A publication Critical patent/DK258082A/en
Publication of DK161172B publication Critical patent/DK161172B/en
Application granted granted Critical
Publication of DK161172C publication Critical patent/DK161172C/en

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
    • G08B13/2422—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 acoustic or microwave tags
    • 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

Abstract

An anti-theft marking 34 containing a semi-conductor diode 36 connected to a metal antenna loop 38 is adapted so as to receive two different radio frequency transmissions. The diode 36 shunts a closed loop in one end of the antenna 38 which forms a tank resonant circuit at double a selected centre frequency. A first transmitter 26 generates a tone-modulated radio frequency f1 shifted to one side of the centre frequency, while a second transmitter 30 generates a continuous RF wave f2 which is shifted to the other side of the centre frequency. Both signals are fed separately to emitting dipole antenna strips 18, 19, 20, 21 on either side of a surveillance area. The dipole strips for the different frequencies are at right angles to one another on each side. The dipole strips for the same frequency are at right angles to the strips on the opposite side. This produces a cross-polarized transmission of both frequencies within the surveillance area. The diode 36 of the marking 34 mixes the two frequencies received by means of the antenna loop 38, as a result of which the tank circuit oscillates at the sum of the two frequencies (double the centre frequency). The resonant frequency is re-emitted to the receiver antenna 22, 24 on each side for detection by means of a very narrow-band receiver 42 which can respond to the resonant frequency. The modulation tone originates from the signal received and is signal-processed for triggering an alarm 44 when the signal detected is of sufficient strength and duration. <IMAGE>
DK258082A 1980-10-09 1982-06-09 PLANT FOR THE DETECTION OF AN OBJECT IN A SURVEY AREA. DK161172C (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US19557280A 1980-10-09 1980-10-09
US19557280 1980-10-09
PCT/US1981/001335 WO1982001437A1 (en) 1980-10-09 1981-10-01 Dual frequency anti-theft system
US8101335 1981-10-01

Publications (3)

Publication Number Publication Date
DK258082A true DK258082A (en) 1982-06-09
DK161172B DK161172B (en) 1991-06-03
DK161172C DK161172C (en) 1991-11-25

Family

ID=22721923

Family Applications (1)

Application Number Title Priority Date Filing Date
DK258082A DK161172C (en) 1980-10-09 1982-06-09 PLANT FOR THE DETECTION OF AN OBJECT IN A SURVEY AREA.

Country Status (12)

Country Link
EP (1) EP0062056A4 (en)
JP (1) JPH0353678B2 (en)
AU (1) AU552568B2 (en)
BR (1) BR8108829A (en)
CA (1) CA1190970A (en)
DK (1) DK161172C (en)
ES (1) ES8207351A1 (en)
FI (1) FI73532C (en)
IT (1) IT1142881B (en)
NZ (1) NZ198497A (en)
WO (1) WO1982001437A1 (en)
ZA (1) ZA816937B (en)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3376703D1 (en) * 1982-04-12 1988-06-23 Ici America Inc Crossed beam high frequency anti-theft system
CA1236542A (en) * 1983-08-02 1988-05-10 Harold B. Williams Electronic article surveillance system having microstrip antennas
US5349332A (en) * 1992-10-13 1994-09-20 Sensormatic Electronics Corportion EAS system with requency hopping
US5347280A (en) * 1993-07-02 1994-09-13 Texas Instruments Deutschland Gmbh Frequency diversity transponder arrangement
US5831530A (en) * 1994-12-30 1998-11-03 Lace Effect, Llc Anti-theft vehicle system
US5798693A (en) * 1995-06-07 1998-08-25 Engellenner; Thomas J. Electronic locating systems
US8358209B2 (en) * 2005-06-03 2013-01-22 Sensomatic Electronics, LLC Techniques for detecting RFID tags in electronic article surveillance systems using frequency mixing

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NO126975B (en) * 1967-03-30 1973-04-16 John Welsh
US3631484A (en) * 1969-07-30 1971-12-28 Microlab Fxr Harmonic detection system
US3707711A (en) * 1970-04-02 1972-12-26 Peter Harold Cole Electronic surveillance system
US3895368A (en) * 1972-08-09 1975-07-15 Sensormatic Electronics Corp Surveillance system and method utilizing both electrostatic and electromagnetic fields
GB1586069A (en) * 1976-11-15 1981-03-18 Nedap Nv Detection systems
NL7804417A (en) * 1977-04-28 1978-10-31 Parmeko Ltd DETECTION SYSTEM FOR MONITORING THE POSITION OF AN ARTICLE IN A CONTROL ZONE.
US4139844A (en) * 1977-10-07 1979-02-13 Sensormatic Electronics Corporation Surveillance method and system with electromagnetic carrier and plural range limiting signals
ZA7994B (en) * 1978-01-11 1980-01-30 Tag Radionics Ltd Presence sensing system
US4249167A (en) * 1979-06-05 1981-02-03 Magnavox Government And Industrial Electronics Company Apparatus and method for theft detection system having different frequencies

Also Published As

Publication number Publication date
EP0062056A4 (en) 1985-06-06
AU7721981A (en) 1982-05-11
NZ198497A (en) 1985-08-30
IT1142881B (en) 1986-10-15
JPH0353678B2 (en) 1991-08-15
FI821956A0 (en) 1982-06-02
WO1982001437A1 (en) 1982-04-29
BR8108829A (en) 1982-08-24
CA1190970A (en) 1985-07-23
FI73532C (en) 1987-10-09
IT8149451A0 (en) 1981-10-08
JPS57501550A (en) 1982-08-26
EP0062056A1 (en) 1982-10-13
DK161172B (en) 1991-06-03
FI73532B (en) 1987-06-30
DK161172C (en) 1991-11-25
ES506117A0 (en) 1982-09-01
ZA816937B (en) 1982-11-24
AU552568B2 (en) 1986-06-05
ES8207351A1 (en) 1982-09-01

Similar Documents

Publication Publication Date Title
US5784021A (en) Noiseless radar detector
GB1440398A (en) Reuduction of false alarms in electronic theft-detection systems
US3863240A (en) Electromagnetic intrusion detection system
DK258082A (en) Theft frequency detector with two frequencies
NO158390C (en) A system for detecting the presence of an object within a surveillance zone.
JPH07141577A (en) Room trespasser detector
GB2289602A (en) Improvements in detection systems
JPS58200187A (en) Detecting method by sensor
US3815130A (en) Near field target discrimination and intrusion detection system
CA1098200A (en) Radar beacon apparatus
RU2032223C1 (en) Antitheft signalling device with detection of marks
JPH0527017A (en) Object detecting device
JPS6439129A (en) Communication equipment facilitating transfer of information between vehicle and stational information spot
JPH04178589A (en) Fm-cw radar device
JP2001264452A (en) Transmission type sensor
KR880002492B1 (en) Dual frequency anti-theft system
KR960006721Y1 (en) Radar monitor supervisor area wireless alarm circuit
KR0175761B1 (en) Frequency Modulation Proximity Warning System
EP0042203B1 (en) Polarization ratiometry object detection system and method
JP3270330B2 (en) Patient detection device
JPH0452585A (en) Target detection device
RU98103672A (en) NQR - A SYSTEM FOR DETECTING MINES AND LUGGAGE CONTROL
JPS5473599A (en) Microwave ingression alarm apparatus
JPH0223835B2 (en)
JPH07110371A (en) Radar radio wave detector

Legal Events

Date Code Title Description
PBP Patent lapsed