Apparatus and method for detecting a magnetic marker
Patent 4710752 Issued on December 1, 1987. Estimated Expiration Date: 
August 8, 2006. 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.
August 8, 2006. 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 3747086 Surveillance method and system with electromagnetic carrier and plural range limiting signals Patent #: 4139844 InventorAssigneeApplicationNo. 06/894429 filed on 08/08/1986US Classes:340/551, Disturbance of magnetic field340/572.2Specified relationship between field and detection frequencies (e.g., nth order harmonics)ExaminersPrimary: Swann, III, Glen R.Attorney, Agent or FirmInternational ClassG08B 13/24 (20060101)AbstractThis invention relates to an apparatus and method for detecting the presence of a magnetic marker in an interrogation zone. A dual frequency magnetic field is generated causing a magnetic marker to produce amplitude modulated side band signals at harmonics of the higher frequency field. These side band signals are readily distinguishable from amplitude noise.Field of SearchDisturbance of magnetic field | |
