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Circuit for selectively exciting one of a pair of light emitting diodes

  • US 4,484,105 A
  • Filed: 10/28/1982
  • Issued: 11/20/1984
  • Est. Priority Date: 10/28/1982
  • Status: Expired due to Fees
First Claim
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1. A circuit for selectively lighting one of a pair of light emitting diodes arranged in a parallel configuration so as to be oppositely poled to conduct current in opposite parallel paths, said circuit comprising:

  • a first photon-responsive device connected to one side of the pair of light emitting diodes;

    a second photon-responsive device connected to an opposite side of the pair of light emitting diodes;

    means for connecting a current source with both photon-responsive devices;

    shunting means connecting across the first photon-responsive device having a resistance value which is substantially greater than the resistance of the first photon-responsive device when it is conducting;

    a first photon-emitting device optically coupled with the first photon-responsive device and connected to the opposite side of the pair of light emitting diodes;

    a second photon-emitting device optically coupled with the second photon-responsive device and connected with the one side of the pair of light emitting diodes; and

    means for selectively connecting ground to the first or second photon-emitting devices such that when ground is connected to the first photon-emitting device current flows from the current source connecting means through the shunting means and the first photon-emitting device driving the first photon-emitting device to emit light to excite the optically coupled first photon-responsive device into conduction thereby producing sufficient current to light one of the pair of light emitting diodes and when ground is connected to the second photon-emitting device current flows through the shunting means and the second photon-emitting device driving the optically coupled second photon-emitting device to emit light to excite the second photon-responsive device into conduction thereby producing sufficient current to light the other of the pair of light emitting diodes.

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