How Wozniak Made the Apple II Display Color Graphics
Steve Wozniak's 1977 patent for a circuit that allowed a home computer to display stable, sharp color graphics on a standard television screen.
Original patent title: “Microcomputer for use with video display”
Steve Wozniak's 1977 patent for a circuit that allowed a home computer to display stable, sharp color graphics on a standard television screen. Granted to Apple Computer Inc in 1979 with 10 claims and 29 forward citations, and it is now in the public domain.
Coverage
What does this patent actually cover?
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.
The gap
What does this patent 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.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
Wozniak realized that if you force the computer's horizontal sync to be an odd-submultiple of the color subcarrier, the phase of the color signal automatically corrects itself every other line, eliminating the need for complex and expensive external hardware.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Apple II personal computer
Early home video game consoles using NTSC television signals
Why it matters
The bigger picture
This patent was the technical backbone of the Apple II, the machine that effectively launched the personal computer industry. By allowing the Apple II to plug into an affordable, off-the-shelf television instead of an expensive professional monitor, Wozniak made home computing commercially viable for the first time.
Filed
April 11, 1977
Granted
January 23, 1979
Market context
Who's building on this
Companies in this space
While this specific hardware approach is largely obsolete due to digital display standards, the legacy of this design lives on in the engineering philosophy of Apple. Modern companies like NVIDIA and AMD continue to solve similar synchronization challenges, though they now manage them through complex GPU driver stacks and high-speed digital interfaces like DisplayPort rather than discrete timing counters.
Market impact
This patent enabled the 'home computer' category by bridging the gap between expensive professional computing gear and consumer television sets. It effectively forced the industry to adopt the Apple II's cost-effective design pattern, proving that a mass-market computer could be both affordable and capable of high-quality color output.
Claim 1 — Plain English
What this patent covers
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.
The clever bit
Wozniak realized that if you force the computer's horizontal sync to be an odd-submultiple of the color subcarrier, the phase of the color signal automatically corrects itself every other line, eliminating the need for complex and expensive external hardware.
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.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
This patent is in the public domain
See the Freedom to Build guide — what is free to use, what is not, and how to cite this patent.
PatentBrief Score
Impact Score
Moderate
Citation count
29/40
Moderately cited
Claim breadth
7/20
Moderate scope
Recency
0/20
Older than 20 years
Assignee scale
20/20
Major company or institution
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$17K – $54K
Midpoint $34K · expired or expiring · industry ×1.5
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Patent Claims
1 independent claim · 0 dependent
Claims are the legal boundaries of the patent. An independent claim stands alone. A dependent claim adds limitations to its parent, narrowing — but not broadening — the scope.
The original legal language
Original claims
10 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Wozniak, S. G. (1979). How Wozniak Made the Apple II Display Color Graphics (U.S. Patent No. 4,136,359). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/4136359/apple-ii-personal-computer
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How Wozniak Made the Apple II Display Color Graphics cover?
Steve Wozniak's 1977 patent for a circuit that allowed a home computer to display stable, sharp color graphics on a standard television screen.
Who owns patent US 4136359?
Apple Computer Inc owns this patent, granted in 1979.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 4136359 cited by?
This patent has been cited by 29 later patents that build on its ideas.
What problem does this patent solve?
This patent was the technical backbone of the Apple II, the machine that effectively launched the personal computer industry. By allowing the Apple II to plug into an affordable, off-the-shelf television instead of an expensive professional monitor, Wozniak made home computing commercially viable for the first time.
What does this patent NOT cover?
Does not cover non-raster scan display technologies like modern LCD or OLED panels.
Same assignee
More from Apple Computer Inc
Patent monitoring