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VEHICLE ALARM SYSTEM

  • US 3,748,494 A
  • Filed: 04/14/1971
  • Issued: 07/24/1973
  • Est. Priority Date: 08/06/1969
  • Status: Expired due to Term
First Claim
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1. A sensing method for an alarm system and comprising the steps of:

  • applying a potential to a diode-connected transistor to provide a first current therein establishing a desired base-emitter voltage therein, applying the base-emitter voltage of saiD diode-connected transistor across a series combination of the base-emitter junction of a second transistor, an impedance, and a portion of a vehicle electrical system, thereby normally maintaining a forward bias on said second transistor to keep it normally conducting, and applying a potential across the combination of said series combination in series with a second impedance, and thereby establishing at said second impedance a voltage dependent on the current in said series combination as influenced and varied by change of resistance of said portion of said vehicle electrical system.

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