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Apparatus for audible alerting of enclosure opening

  • US 4,155,077 A
  • Filed: 04/06/1977
  • Issued: 05/15/1979
  • Est. Priority Date: 04/06/1977
  • Status: Expired due to Term
First Claim
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1. A portable miniaturized self-contained audible alerting apparatus for being placed in a normally darkened enclosure for audibly alerting a person outside of and a distance from said enclosure that said enclosure is opened, said apparatus comprising a small case having a light-receiving aperture, photodetector means within said case and positioned with respect to said aperture for detecting light received by said aperture and providing a first signal which is electronic and of an inaudible character in response to detected light, time delay means within said case for providing a time-delayed second signal in response to the persistence of said first signal for a predetermined period, said time delay means including a first logic inverting gate having an input interconnected with said photodetector means, a resistor interconnecting the output of the first logic inverting gate to at least one input of a second logic inverting gate, and a capacitor interconnected with said input of the second logic gate and adapted for being charged through said resistor, the output of the secnd logic inverting gate providing said time-delayed second signal, amplifier means within said case for effectively amplifying said time-delayed second signal, and audible signaling means within said case and responsive to the amplified second signal for providing an audible alerting signal of sufficient loudness for being heard by said person outside of and at a distance from said enclosure, said case including within it a battery for powering said time delay means, said amplifier means, and said audible signaling means, said case being positionable within said enclosure for permitting light outside said enclosure to be received by said aperture when said enclosure is opened whereby if said enclosure is opened, said person will be alerted after said predetermined period by said audible alerting signal, said time delay means being operative for preventing said alerting signal from being given if said enclosure is not opened for the predetermined period, said first signal being terminated when light is no longer detected by said photodetector means, said audible alerting signal ceasing after light is no longer detected by said photodetector means.

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