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Device for preventing an electrical equipment from re-powering after recovery of service interruption

  • US 5,723,914 A
  • Filed: 04/26/1996
  • Issued: 03/03/1998
  • Est. Priority Date: 04/28/1995
  • Status: Expired due to Term
First Claim
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1. A security device for electrical equipment having a power switch, the electrical equipment being connected to a power source in use, said device comprising:

  • a first voltage detection circuit, operable under a first condition when the electrical equipment is supplied with power from the power source, for detecting a voltage of the power source and outputting a first detection voltage;

    a second voltage detection circuit, operable under a second condition when the electrical equipment is supplied with power from the power source and when the power switch is turned on to allow the electrical equipment to be powered by the power source, for detecting a voltage of the power source and outputting a second detection voltage;

    a comparator connected to said first voltage detection circuit to receive the first detection voltage and also connected to said second voltage detection circuit to receive the second detection voltage, said comparator comparing the first detection voltage with the second detection voltage and outputting a comparison result, said comparison result differing depending on whether said power source is operating under a normal powering condition or whether power has been restored following a power disruption while said power switch is in a closed position; and

    control means for controlling the electrical equipment so as not to be powered by the power source in response to the comparison result obtained after power has been restored following a power disruption while said power switch is in a closed position.

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