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Alpha-numeric-display system with selectable crawl

  • US 4,320,395 A
  • Filed: 03/10/1980
  • Issued: 03/16/1982
  • Est. Priority Date: 03/12/1979
  • Status: Expired due to Term
First Claim
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1. In a method for displaying an alpha-numeric text in a horizontal line on a face of a television monitor, wherein sequential characters of said text move across said face in a fixed spatial relationship to one another, said characters being prestored in coded form and subsequently decoded into binary signals combined with horizontal and vertical sync pulses and fed to the receiving terminals of said monitor for effectuating the display of said text, signals corresponding to a first character in a horizontal scan being emitted only upon the elapse of a delay time following said horizontal sync pulses, said characters having on said face a common apparent character width correponding to a horizontal-scanning interval TZ substantially less than an interval between consecutive horizontal sync pulses, the improvement comprising the steps of:

  • generating a frequency fG which is at least equal to the reciprocal of said interval TZ ; and

    successively decreasing, upon said vertical sync pulses, said delay time by an increment TG to implement motion of said characters across said face, said increment TG being equal to the period of said frequency fG andcontrolling said width by application of a horizontal sampling frequency fZ whose period is equal to said interval TZ, said frequency fG being an integral multiple of said sampling frequency fZ.

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