Pre-intrusion detection device
Patent 4168495 Issued on September 18, 1979. Estimated Expiration Date: 
October 11, 1997. 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.
October 11, 1997. 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 2094351 3440633 3623063 3771152 Capacitor detector device Patent #: 3973208 InventorAssigneeApplicationNo. 05/840911 filed on 10/11/1977US Classes:340/546, Portable331/65, WITH DEVICE RESPONSIVE TO EXTERNAL PHYSICAL CONDITION340/562CapacitanceExaminersPrimary: Swann, III, Glen R.Attorney, Agent or FirmInternational ClassesG08B 13/26 (20060101)G08B 13/22 (20060101) AbstractAn intrusion detection unit comprises a compacitance having an "active" field, the coupling of which is significantly increased when an intruder comes into conductive relation with a doorknob. The unit is hung on the inside doorknob and is so arranged that the doorknob is the transmitting element of the capacitor, while a separate plate is the receiving element of the capacitor. The capacitor field is maintained actively charged by a battery driven oscillator which operates at a substantially uniform frequency and amplitude. The intrusion detector circuit is complete in itself and is not externally grounded by the intruder. The signal receiving portion of the circuit incorporates a square law amplifier, and also has means for adjusting the reference level to which the signal is compared.Field of SearchCapacitance | |
