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.

What it 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 it doesn't 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.

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.

Why it matters

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.

Real-world examples

• 1.Hamilton Pulsar (1972)