Method and apparatus for selective electronic surveillance
Patent 4212002 Issued on July 8, 1980. Estimated Expiration Date: 
March 3, 1998. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
March 3, 1998. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3707711 3895368 Theft detection system Identification of vehicles Article detection system with near field electromagnetic wave control Method and apparatus for electronic surveillance of precisely defined control zone Surveillance method and system with electromagnetic carrier and plural range limiting signals Patent #: 4139844 InventorApplicationNo. 05/883058 filed on 03/03/1978US Classes:340/572.4, Specified processing arrangement for detected signal340/505, Interrogator-responder340/572.5Having tuned resonant circuitExaminersPrimary: Swann, III, Glen R.International ClassG08B 13/24 (20060101)AbstractA high frequency (HF) generator projects an electronic wave into a surveillance area to establish a first field. At least one control zone is set up within the surveillance area by two frequency modulated (FM) generators. The first FM generator establishes a second field in the control zone. The second FM generator establishes a third field only at a control zone margin, thereby defining the limits of the control zone. Presence within the control zone of a transponder cause reradiation of a signal comprised of the high frequency and FM signal, which provides an output signal. Additional control zones may be set up within the surveillance area by the addition of further FM generators.Field of SearchInterrogator-responder | |
