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Security device for motor vehicles and other d.c. electrical systems

  • US 4,323,878 A
  • Filed: 09/22/1980
  • Issued: 04/06/1982
  • Est. Priority Date: 09/22/1980
  • Status: Expired due to Term
First Claim
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1. A security device for use with a d.c. electrical system including a d.c. source, said device comprising an alarm element connected across said source, relay means including a relay coil and a normally open relay switch, said relay switch being connected to said alarm element to actuate the latter on energization of said relay coil, switch means connected to said relay coil to maintain the latter de-energized in the stand-by condition and energized in the alarm condition, operating means connected to said d.c. source and said switch means to maintain the latter open responsive to constant voltage of said source and effect closing of said switch means responsive to lowered voltage of said source, and delay means controlling the time required by said operating means to assume its open switch means maintaining condition, said relay including an additional relay switch adapted to close and open with said first mentioned relay switch, and timer means connected to said additional relay switch and said switch means for opening the latter and de-energizing the relay coil after a predetermined interval to open said first mentioned and additional relay switches and stop actuation of said alarm element.

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