ELECTRONIC SURVEILLANCE SYSTEM

• US 3,755,803 A
• Filed: 03/31/1970
• Issued: 08/28/1973
• Est. Priority Date: 04/02/1969
• Status: Expired due to Term

• Current Assignee: Peter Harold Cole, Richard Vaughn
• Original Assignee: Peter Harold Cole, Richard Vaughn
• Inventors: Cole, Peter Harold, Vaughn, Richard
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Partridge, Scott F.
• Application Number:
  US05/024,319
• Time in Patent Office: 1,246 Days
• Field of Search: 340/258,280,282,2 343/6.5,6.8 331/155,158 310/8.1,8.2
• US Class Current: 340/572.1
• CPC Class Codes: G06K 19/0672 with resonating marks
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/02 by pneumatic or hydraulic means, e.g. sensing punched holes with compressed air; by sonic means ; by ultrasonic means
• CPC Class Codes: G06K 7/086 sensing passive circuit, e.g. resonant circuit transponders
• CPC Class Codes: G06K 7/10009 sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
• CPC Class Codes: G08B 13/24 by interference with electromagnetic field distribution
• CPC Class Codes: G08B 13/2422 using acoustic or microwave tags
• CPC Class Codes: G08B 13/2437 Tag layered structure, processes for making layered tags
• CPC Class Codes: G08B 13/2471 Antenna signal processing by receiver or emitter

Abstract

An electronic surveillance system in which a passive label attached to an article under surveillance is interrogated by means of a transmitted signal in a first form of energy, the label using the energy of that signal to return a signal to a receiver which gives an indication of the presence of the label if a reply signal has predetermined characteristics. In order to enable the receiver to distinguish the reply signal from the original transmitted signal the label is constructed to produce the reply signal in a form of energy different from that of the original transmitted signal. It is preferred that the first form of energy is accoustic energy and the second form of energy is electromagnetic energy.

Claims

1. An electronic surveillance system, comprising transmitter means for transmitting signals having a first form of energy, a passive label for attachment to an article to be placed under surveillance, signal answering means mounted on said label for receiving the signals from said transmitting means and producing signals having a second form of energy and corresponding to the received signals, receiver means responsive to the signals transmitted by said signal answering means for receiving and processing the signals of the second form of energy, control means for defining a surveillance volume, said control means including modulator means coupled to said transmitter means and rendering said receiver means unresponsive to signals from said answering means when the phase of the signals from said answering means relative to the phase of signals from said transmitter means exceeds a given value.

2. A system as in claim 1, wherein said modulator means constrains said transmitter means to produce a series of regular pulses and gate said receiver means synchronously so as to switch on said receiver means at a predetermined time after the commencement of each transmitter pulse and for a predetermined period.

3. A system as in claim 1, wherein one of said transmitter means and said answering means transmit acoustical energy.

4. A system as in claim 1, wherein said transmitter means transmits acoustical energy.

5. A system as in claim 1, wherein said answering means transmits acoustical energy.

6. A system as in claim 4, wherein said answering means transmits electromagnetic energy.

7. A system as in claim 5, wherein said transmitter means transmits electromagnetic energy.

8. A system as in claim 1, wherein said answering means includes second receiver means on said label for receiving the signals of the first form of energy, transducer means on said label coupled to said receiver means for responding to the signals on said second receiver means for forming signals of the second form of energy, and second transmitter means on said label responsive to said transducer means for transmitting the signals of the second form of energy.

9. A system as in claim 1, wherein said answering means includes an electroacoustic resonator on said label.

10. A system as in claim 9, wherein said resonator is piezoelectric.

11. A system as in claim 9, wherein said resonator is magnetostrictive.

12. An apparatus as in claim 10, wherein said answering means includes an antenna connected to said resonator.

13. A system as in claim 1, wherein said label includes a plastic card having a cutout, said answering means including a piezoelectric resonator adapted to vibrate in a flexural mode, said resonator including electrodes attached to the surface of said piezoelectric resonator, and an antenna formed on the surface of the card connected to said electrodes.

14. A system as in claim 13, wherein said label includes covering means sandwiching the plastic card between them for protecting the resonator and said antenna.