[time-nuts] How did they distribute time in the old days?
bownes at gmail.com
Wed Oct 14 17:09:19 EDT 2015
And to tie this back to the UPS thread, at university, the Simplex clock sync signal made our Vax 11/730 TOD clock run waaaay fast.
I never figured out if it was using line frequency zero crossings for seconds or if it was leaking as DEC fixed it not long after it was installed. (And it was moved to a different phase of the power system than the clocks...)
> On Oct 14, 2015, at 15:55, Jim Harman <j99harman at gmail.com> wrote:
> The Western Union clocks were still in use at broadcast stations in the
> early 1970s. One problem was that the reset pulse and resulting jump in
> time would come exactly on the hour, when you were trying to synchronize
> with a network news broadcast that began at the network's version of 00:00.
> ABC and I presume the other networks would send a tone 10 seconds before
> their program started, By listening to the network on the "Cue" channel,
> you would have a pretty good idea of when the news would start.
> Another system in wide use around then and still somewhat today for
> controlling the clocks in a large building was sold by Simplex. The
> building would have a master clock (set manually by the custodian or
> whoever) that pumped out tones at about 3 KHz over the power lines. These
> signals would come out a couple of minutes before the hour, presumably to
> avoid problems with events scheduled on the hour. The slave clocks were
> designed to run a little fast, and would wait at 58:00 until they received
> a tone to restart. I believe there was a special tone that would make the
> clock run "fast forward," to deal with longer adjustments for power outages
> and DST.
> One drawback of this system is that the tones sometimes leak into audio
> equipment, and in a quiet room they are often audible through the
> fluorescent light ballasts.
> On Wed, Oct 14, 2015 at 12:42 PM, Nick Sayer via time-nuts <
> time-nuts at febo.com> wrote:
>> The WU standard time service goes back further than the turn of the 20th
>> century. It started in 1870.
> --Jim Harman
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
More information about the time-nuts