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Circuit arrangement for automatically closing a switching transistor for a predetermined time period after opening a switching means

  • US 4,172,221 A
  • Filed: 05/18/1977
  • Issued: 10/23/1979
  • Est. Priority Date: 05/19/1976
  • Status: Expired due to Term
First Claim
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1. A circuit arrangement for energizing a load device for a predetermined time period after operation of a switch, comprising:

  • a radiation emissive element, connected in series with said switch between first and second terminals of a voltage source, for emitting radiation in response to a first circuit condition of said switch;

    a radiation responsive element having a resistance which varies instantaneously from a normal value in response to receipt of the emitted radiation and gradually returns to the normal value as a function of time in response to the absence of said radiation, said radiation responsive element being connected in series with a resistance element between said first and second voltage source terminals; and

    a transistor having a control electrode connected to be responsive to the voltage at a junction between said radiation responsive element and said resistance element, said control electrode being responsive to the voltage at the junction to cause the transistor to assume first and second switching states in response to said voltage being respectively below and above a predetermined threshold level,whereby there is a transition of a voltage in said circuit arrangement from first to second voltage levels in response to said switch being switched to a second circuit condition and there is a transition of said voltage from said second to first voltage levels in response to said transistor assuming said second switching state.

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