Nick Sayer writes: > The WU standard time service goes back further than the turn of the 20th > century. It started in 1870.
See also: http://leapsecond.com/history/usno.htm > I’ve always wanted to get my hands on one of those clocks and come up with a > circuit to recreate > the synchronization signal for it, probably with a Raspberry Pi running ntpd > and a big ol’ MOSFET. > The problem is that at this point, those clocks are quite expensive once > they’re reconditioned. You will find lots of these auto-setting self-winding clocks on eBay. Some are very reasonably priced. There's a bunch of clock guys out there who play with these and you'll find circuits and information with a google search for words like self-winding clock company or SWCC or Western Union USNO and so on. Start with: https://en.wikipedia.org/wiki/Self_Winding_Clock_Company http://www.telechron.com/swcc/swcc.html http://www.kensclockclinic.com/pdf/PoweringSWC.pdf http://community.nawcc.org/chapter52/pages/selfwindingclockco Mitch's (www.telechron.com) and Ken's (www.kensclockclinic.com) sites are superb. Also, for a screen full of irresistible SWCC photos, try this: https://www.google.com/search?tbm=isch&q=self-winding+clock+company > My understanding (perhaps incorrect) was that the sync pulse was once daily > and, as you said, > would cause the hands to “snap” to 12. The trailing edge of the pulse was > synchronized and would > release the clock to operate normally. > > That they had something as accurate and widespread as it was so early is > astonishing. Oh, Padawan, that's just the tip of the iceberg when it comes to the deep and fascinating history of precise timekeeping. /tvb _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.