Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1981-04-24
1984-05-15
Swann, III, Glen R.
Communications: electrical
Condition responsive indicating system
Specific condition
331 65, 331158, G08B 1326, G08B 2100
Patent
active
044491220
ABSTRACT:
A proximity detector includes a crystal which is coupled to an impedance circuit having a value selected to sustain or prevent oscillation of the crystal. At selected points in the impedance circuit, a sensing line is coupled to add capacitance to initiate or terminate crystal oscillation. A detector circuit coupled to the amplified output of the oscillator signal is used to control an alarm circuit. By coupling the sensing line so that capacitance is added to the impedance circuit when the proximity of an individual or other animal tissue is sensed, oscillation of the crystal is initiated or terminated to control the alarm circuit. The oscillator circuit provides improved stability and sensitivity for use of the circuit in a variety of environments.
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