Hamilton's Early Digital Watch with LED Display
Hamilton's 1972 patent for a digital watch that uses electronic circuits and light-emitting diodes (LEDs) to show time, instead of gears and hands, powered by a rechargeable battery.
Original patent title: “Solid state watch”
Hamilton's 1972 patent for a digital watch that uses electronic circuits and light-emitting diodes (LEDs) to show time, instead of gears and hands, powered by a rechargeable battery. Granted to Hamilton Watch Co in 1972 with 23 claims and 118 forward citations, and it is now in the public domain.
Key facts
Coverage
What does this patent actually cover?
This patent describes a digital watch with no moving parts for telling time. It uses a crystal-controlled oscillator to create precise timing signals. These signals are then processed by an integrated circuit that divides the frequency and drives light-emitting diodes (LEDs). The LEDs form a digital display, showing hours, minutes, and seconds in base-ten numbers. A key feature is a 'demand switch' that only turns on the LEDs when pressed, saving battery power. Another innovation is an ambient light sensor that adjusts the brightness of the LEDs based on surrounding light conditions. The whole system is powered by a rechargeable battery.
The gap
What does this patent NOT cover?
- Watches that use mechanical gears and hands to display time.
- Watches that use analog displays instead of digital numbers.
- Watches that do not have a crystal-controlled oscillator for timing.
- Watches that do not use light-emitting diodes for display.
- Watches where the display is always on without a demand switch.
- Watches that do not adjust display brightness based on ambient light.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
The invention cleverly combined a stable crystal oscillator with integrated circuits and an LED display, all managed by a 'demand' system and ambient light control, to create a completely solid-state, power-efficient digital watch.
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
Hamilton Pulsar (1972)
Why it matters
The bigger picture
This patent represents an early step towards modern digital watches and electronic timekeeping. The Hamilton Pulsar, based on this technology, was one of the first digital wristwatches available to consumers, marking a significant shift from traditional mechanical watches.
Filed
May 6, 1970
Granted
June 27, 1972
Market context
Who's building on this
Companies in this space
While the specific technology of early LED watches has been largely superseded, the foundational concepts of using crystal oscillators, integrated circuits for timekeeping, and digital displays are fundamental to virtually all modern electronic watches and timekeeping devices produced by companies like Apple, Samsung, and Casio.
Market impact
This patent was instrumental in the launch of the Hamilton Pulsar, one of the first fully digital LED watches. It helped establish a new category of electronic timepieces and signaled the beginning of the end for purely mechanical watches in mainstream consumer markets.
Claim 1 — Plain English
What this patent covers
This patent describes a digital watch with no moving parts for telling time. It uses a crystal-controlled oscillator to create precise timing signals. These signals are then processed by an integrated circuit that divides the frequency and drives light-emitting diodes (LEDs). The LEDs form a digital display, showing hours, minutes, and seconds in base-ten numbers. A key feature is a 'demand switch' that only turns on the LEDs when pressed, saving battery power. Another innovation is an ambient light sensor that adjusts the brightness of the LEDs based on surrounding light conditions. The whole system is powered by a rechargeable battery.
The clever bit
The invention cleverly combined a stable crystal oscillator with integrated circuits and an LED display, all managed by a 'demand' system and ambient light control, to create a completely solid-state, power-efficient digital watch.
What it does not cover
- Watches that use mechanical gears and hands to display time.
- Watches that use analog displays instead of digital numbers.
- Watches that do not have a crystal-controlled oscillator for timing.
- Watches that do not use light-emitting diodes for display.
- Watches where the display is always on without a demand switch.
- Watches that do not adjust display brightness based on ambient light.
Patent Journey
From filing to expiry
PatentBrief Score
Impact Score
Moderate
Citation count
40/40
Highly cited
Claim breadth
15/20
Broad claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
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
$73K – $234K
Midpoint $146K · 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.
The original legal language
Original claims
23 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Bergey, J. M., & Walton, R. S. (1972). Hamilton's Early Digital Watch with LED Display (U.S. Patent No. 3,672,155). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/3672155/digital-watch-pulsar
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 Hamilton's Early Digital Watch with LED Display cover?
Hamilton's 1972 patent for a digital watch that uses electronic circuits and light-emitting diodes (LEDs) to show time, instead of gears and hands, powered by a rechargeable battery.
Who owns patent US 3672155?
Hamilton Watch Co owns this patent, granted in 1972.
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 3672155 cited by?
This patent has been cited by 118 later patents that build on its ideas.
What problem does this patent solve?
This patent represents an early step towards modern digital watches and electronic timekeeping. The Hamilton Pulsar, based on this technology, was one of the first digital wristwatches available to consumers, marking a significant shift from traditional mechanical watches.
What does this patent NOT cover?
Watches that use mechanical gears and hands to display time.
Patent monitoring