3 ms·
Meanwhile, in the USA, Western Union used their telegraph network to build out a system of synchronized clocks. A long pulse on the line at the top of the hour
by joezydeco 4y ago
Meanwhile, in the USA, Western Union used their telegraph network to build out a system of synchronized clocks. A long pulse on the line at the top of the hour engaged a solenoid in the clock that pulled the minute hand back to :00.
https://hackaday.com/2019/09/25/100-year-old-atomic-clock/ https://hackaday.com/2019/09/25/100-year-old-atomic-clock/
And, since this is HN, it's worth mentioning that this was a subscription service.
- whatshisface 4y agoSince the speed of sound is lower in tubes, I wonder how late the clocks were at the end of the network.
- hulitu 4y agoAs far as i understand the signal was transmitted through telegraph lines, not tubes.
- joezydeco 4y agoIf you're referring to the pneumatic network, one of the footnotes mentions a latency of 10 seconds, but the author does the math and says that's probably not accurate, more like 58 seconds at the 20km max distance. http://www.douglas-self.com/MUSEUM/COMMS/airclock/airclock.htm http://www.douglas-self.com/MUSEUM/COMMS/airclock/airclock.h...
- jbay808 4y agoThe article doesn't seem to mention it, but the clocks were each offset to compensate for the propagation delay. It's a static correction, so easily done by just offsetting the minute hand position. (I can't seem to find the citation on this, though.)
- jonny_eh 4y agoIt's amazing that Western Union didn't lobby congress to ban free, government operated, time synchronization services.
- joezydeco 4y agoProbably didn't need to. WU had the monopoly on cross-continent communication lines. The government didn't have the resources to compete.
- jonny_eh 4y agoI was actually referencing: https://qz.com/1913544/telecom-lobbyists-stop-cities-from-building-fiber-optic-networks/ https://qz.com/1913544/telecom-lobbyists-stop-cities-from-bu...