[time-nuts] 1903 Railroad self-Winding / Self-setting Clock: rapid clicking

paul swed paulswedb at gmail.com
Sun Nov 2 12:08:06 EST 2014

Pretty funny. As a ham radio operator I have had 4 clocks on the walls for
I obtained 5 IBM clocks quite a while ago and built drivers and such for
them. Actually ran them for a while but found the noise annoying. Replaced
them with cheap wall clocks internal drivers removed and a master system
that drives them. NOT connected to GPS since its really just a relative
thing. Is it dark in the UK or Japan. This has been running about 10 years
and I do correct the time at the DST switch and occasionally in between.
But its a stable low power thing that runs for months on C cells if the
mains go away.

On Sun, Nov 2, 2014 at 6:36 AM, Mitchell Janoff <majanoff at verizon.net>

> The rapid clicking of slave clocks in schools was a design feature of IBM
> (and later Simplex) clocks. The master clock sent out minute pulses to the
> slave clocks for the first 50 minutes of each hour on the "A" side of the
> circuit. Slave clocks operating on-time would automatically switch to the
> "B" side of the circuit and wait for the 51st minute pulse on the "B" side.
> Slave clocks operating slowly would remain on the A side and receive pulses
> at a rate of 1 every 2 seconds until they automatically switched to the "B"
> side at 50 minutes past the hour. Slave clocks that were running fast
> arrived at 50 minutes past the hour prior to the master and switched to the
> "B" and waited for the next pulse on the "B" side at 51 minutes past the
> hour. On the hour all the slave clocks switched back to receive the hour
> pulse on the "A" side. This was all accomplished by a cam in each of the
> slave clocks that moved a switch from the "A" side to the "B" side. For
> power outages (the master clock coul
>  d continue to operate on a spring or weights but could not send out the
> impulses), the master clock could be fitted with an optional accumulator
> that counted the missed pulses. When power was restored, the accumulator
> would "unwind", sending out rapid pulses until the slaves could catch up.
> This could also be used to move the clocks ahead 23 hours (retard by 1
> hour), or ahead  hour for daylight saving time. Therefore the
> click-click-click in the classrooms as slow slave clocks caught up to the
> master.
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