[time-nuts] Re: Crazy Clock

[Paul Berger]

On 2022-12-15 20:57, Lux, Jim via time-nuts wrote:
>
>
> There are clocks that pulse forward with one polarity, and reset to 
> "top of the hour or day" with a negative pulse.  My middle school had 
> them in the 1970s, and it was interesting to watch the reset cycle (at 
> noon).  Or, to be honest, it might be some sort of "power switching" 
> protocol. That is, use 60 Hz to run, but some pattern of interruption 
> sets it to a known time.  But I remember watching the minute hand snap 
> to 12, then advance in discrete steps.
>
>
That sounds like an impulse clock that would use a DC pulse from a 
master clock to pick a solenoid that operated a ratchet mechanism that 
advanced the minute hand and the hour hand was gear driven off of it.  I 
have an old IBM impulse clock that used a 24 VDCÂ  pulse to advance the 
minute hand.  Over the ratchet wheel there is a two way contact that is 
operated by a bump on the ratchet wheel that would disconnect the normal 
pulse at 1 minute before the hour.  There where both two wire and three 
wire system, mine is wired for the three wire so the top normally open 
contact is connected to the third wire, so with it stopped at 1 minute 
to the hour, a pulse on the third wire would advance the clock on step 
and the normally closed contact would close again and it would 
continue.  On the two wire system there is a diode in series with   I 
believe the normally open contact and the signal line so that when the 
normally open is closed, it will only advance when a pulse of reverse 
polarity is applied.

There was a later system that used clocks with a synchronous motor and 
used signals superimposed on the AC line to synchronize the clocks.  
These clock are easy to recognize as they have a second hand where as 
the impulse clocks do not.

It should also be noted that IBM did make wall clocks that that where 
just normal AC clocks that where not part of a system, like the 15" one 
in front of me built at the IBM Canada plant in Don Mills in the 50s and 
still runs great although there is a little slop in the gears now.

I believe the impulse system was initially developed by International 
Time Recorder (ITR) one of the predecessor companies that was merged  to 
form CTR later renamed to IBM.  IBM would later sell it timeclock 
division to Simplex that continued to produce many of the same designs.

Paul.