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Display unit of speedometer for automobile

  • US 4,647,901 A
  • Filed: 04/13/1983
  • Issued: 03/03/1987
  • Est. Priority Date: 04/20/1982
  • Status: Expired due to Fees
First Claim
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1. A display unit of a speedometer for an automobile, comprising:

  • a constant speed running circuit capable of producing output signals indicative of a desired car speed;

    an actual car speed operational circuit capable of producing output signals indicative of actual car speed;

    a comparing circuit for comparing the amplitudes of said output signals of said constant speed running operational circuit and said actual car speed operational circuit;

    bar graph decoders receiving said output signals from said constant speed running operational circuit and said actual car speed operational circuit;

    an EX-OR circuit having inputs coupled to respective bar graph decoders and having an output;

    an OR circuit having inputs coupled to respective bar graph decoders and having an output;

    selector means coupled to said output of said EX-OR circuit and said output of said OR circuit and controlled by an output of said comparing means for connecting a selected of said outputs of said EX-OR and OR circuits to an output of said selector means; and

    a bar graph display comprising plural display segments and a driving circuit for activating selected of said segments, said driving circuit coupled to the output of said selector means such that said display segments are selectively driven by the output of said EX-OR circuit or the output of said OR circuit;

    whereby said display device displays said desired car speed and actual car speed in two modes, including a first mode in which said display device displays desired car speed and actual car speed by selectively driving display segments corresponding thereto and a second mode in which said display device displays actual car speed and desired car speed by driving selected display segments corresponding to a maximum value of said actual car speed and said desired car speed and indicates at least one segment common to both said actual car speed and desired car speed by inhibiting driving of said at least one display segment.

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