> On Oct 14, 2015, at 4:42 AM, billriches <bill.ric...@verizon.net> wrote: > > Not milisecond time distribution but time related! > > In the early half of the 1900s Western Union was in the time business. They > would rent businesses such as banks, office buildings, etc clocks for a few > dollars a month. These were pendulum wall clocks that had 2 #6 dry cell > batteries inside that would wind them every hour or so. The clocks were > connected to the WU telegraph line and for a minute before and after the > top of the hour all traffic on the circuit would stop. Exactly at the top > of the hour they would push a pulse of 50 ? volts or so over the line and it > would reset the clock to the top of the hour.
The WU standard time service goes back further than the turn of the 20th century. It started in 1870. 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. 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. _______________________________________________ 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.
