{
  "patent_number": "US 4136359",
  "country": "US",
  "title": "How Wozniak Made the Apple II Display Color Graphics",
  "original_title": "Microcomputer for use with video display",
  "summary": "Steve Wozniak's 1977 patent for a circuit that allowed a home computer to display stable, sharp color graphics on a standard television screen.",
  "what_it_does": "This patent describes a timing circuit that synchronizes a computer's digital signals with the analog signal requirements of a standard television. Because televisions use a specific color frequency (the color subcarrier), simply outputting digital data often resulted in blurry or 'crawling' colors. Wozniak's invention uses a horizontal synchronization counter that is locked to an odd-submultiple of the color frequency. By introducing a specific 'delayed' count into this cycle, the system ensures that the color phase remains consistent across different scan lines, preventing the color distortion that would otherwise occur on a consumer CRT display.",
  "what_it_does_not_cover": [
    "Does not cover non-raster scan display technologies like modern LCD or OLED panels.",
    "Does not cover software-based color generation methods that do not rely on hardware-level timing synchronization.",
    "Does not cover high-definition (HD) or 4K signal timing protocols.",
    "Does not cover the specific logic used to store the pixel data itself, only the timing synchronization for the output."
  ],
  "filed": "1977-04-11",
  "granted": "1979-01-23",
  "expires": "1997-04-11",
  "status": "expired",
  "holder": "Apple Computer Inc",
  "holder_url": "https://patentbrief.org/company/apple-computer-inc",
  "inventors": [
    {
      "name": "Stephen G. Wozniak",
      "url": "https://patentbrief.org/inventor/stephen-g-wozniak"
    }
  ],
  "times_cited": 29,
  "tags": [
    "consumer_electronics",
    "semiconductors"
  ],
  "abstract": "A microcomputer including a video generator and timing means which provides color and high resolution graphics on a standard, raster scanned, cathode ray tube is disclosed. A horizontal synchronization counter is synchronized at an odd-submultiple of the color subcarrier reference frequency. A \"delayed\" count is employed in the horizontal synchronization counter to compensate for color subcarrier phase reversals between lines for the non-interlaced fields. This permits vertically aligned color graphics without substantially altering the standard horizontal synchronization frequency. Video color signals are generated directly from digital signals by employing a recirculating shift register.",
  "url": "https://patentbrief.org/patent/us/4136359/apple-ii-personal-computer",
  "markdown_url": "https://patentbrief.org/patent/us/4136359/apple-ii-personal-computer/md",
  "google_patents_url": "https://patents.google.com/patent/US4136359",
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}