Precision time is ubiquitous today thanks to GPS and WWVB. Even your Macbook or smartphone displays time which is synchronized to the NIST-F1 clock, a cesium fountain atomic clock (aka the ‘Atomic Clock’) that is part of a global consortium of atomic clocks known as Coordinated Universal Time (UTC). Without precise timing there would be train collisions, markets would tumble, schools would not start on time, and planes would fall out of the sky.

But how was precision timing achieved in the 19th century during the era of steam, brass, and solenoids? One of the first systems of precision timing kept trains running safely and on time, rang the bells at school, and kept markets trading by using a special clock designed by the Self Winding Clock Company. Through measurements of celestial objects by the US Naval Observatory, and time synchronization pulses broadcast by the Western Union telegraph network, this system synchronized time across the United States in an era where the speed of our train system was out-pacing by the precision of our clocks.

Those clocks were designed so well that many of them are still around and functioning. One of these 100-year-old self-winding clocks made its way onto my workbench. I did what any curious hacker would do, figured out how the synchronization worked and connected it to a clock source with atomic precision. Let’s take a look!

Clock Synchronization That Was Ahead of Its Time

The world changed at the 1893 Columbian Exposition; electricity came of age, tens of thousands of lightbulbs adorned buildings, AC won the battle of the currents, and a system of precisely synchronizing clocks across the entire United States was introduced by the Self Winding Clock Company.

Day-to-day precise timing was provided by the US Naval Observatory in Washington DC who would measure the solar transit of either Mercury or Venus to synchronize the observatory master clock (there were three of them to check the others). This served as the master clock of the entire United States. This official time was transmitted to Western Union for re-transmission via the Western Union network to the regional and local offices.

A time synchronization pulse would be transmitted from the local Western Union office once per hour at the ‘top of the hour’ to customers who were subscribed to the synchronization service. Each customer would pay $1.25 per month per self-winding clock — some subscribers would only synchronize one clock but there were also entire buildings, offices, factories, schools, and train stations connected to the service.

The block diagram below shows a master clock receiving synchronization signals from Western Union. With precise timing, the master clock controls a plurality of secondary clocks.

<img width="176" height="250" src="https://hackaday.com/wp-content/uploads/2019/09/self-winding-clk1.png?w=176" alt="" srcset="https://hackaday.com/wp-content/uploads/2019/09/self-winding-clk1.png 2168w, https://hackaday.com/wp-content/uploads/2019/09/self-winding-clk1.png?resize=176,250 176w, https://hackaday.com/wp-content/uploads/2019/09/self-winding-clk1.png?resize=282,400 282w, https://hackaday.com/wp-content/uploads/2019/09/self-winding-clk1.png?resize=440,625 440w" sizes="(max-width: 176px) 100vw, 176px" data-attachment-id="376402" data-permalink="https://hackaday.com/2019/09/25/100-year-old-atomic-clock/self-winding-clk1/" data-orig-file="https://hackaday.com/wp-content/uploads/2019/09/self-winding-clk1.png" data-orig-size="2168,3077" data-comments-opened="1" data-image-meta='{"aperture":"0","credit":"","camera":"","caption":"","created_timestamp":"0","copyright":"","focal_length":"0","iso":"0","shutter_speed":"0","title":"","orientation":"0"}' data-image-title="self winding clk1" data-image-description="" …read more

Source:: Hackaday