You can freely build on Hamilton's Early Digital Watch with LED Display

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.

What is now free to use

All 1 claims of US 3672155 are in the public domain. Specifically:

The 1 dependent claim add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• 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.

Who is building on this today

While the specific technology of early LED watches has been largely superseded, the foundational concepts of using crystal oscillators, integrated circuits for timekeeping, and digital displays are fundamental to virtually all modern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.

Products built on expired version of this technology

How to cite this patent in your documentation

Hamilton Watch Co. US Patent 3672155. Solid state watch. Granted 1972, expired 1990. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.