I would suggest perhaps the clock in question was not synchronous with
the power system but a "slave" clock which may have been tied to a
master clock ,which may have been synchronous to the power system (most
of the time). The master clock could send extra pulses to advance slave
clock(s) to advance thee time. I don't think the power main could change
frequency a drastic amount.
On 11/29/2015 12:09 PM, Robert Cham wrote:
> I watched it happen. CVPS was known at the time as your part time
> power company. Not the best by any means.
>> What is your source for this ?
>> I think almost all utility power generation equipment is heavy (as in
>> massive) and there is no "jumping" going on. Only slow variations.
>> Who told you about jumping three minutes at noon?
>> I do remember sitting in public school in Toronto in the 60's and
>> watching the wall clock above the door advance an hour very quickly
>> after day light savings switch. I was impressed. Usually I thought
>> the clock was running very slowly.
>> I assume they were no connected to the mains but a separate line
>> which could be used to advance or retard them.
>> On 11/28/2015 10:47 AM, Robert Cham wrote:
>>> In the mid '80s in central Vermont, the frequency was highly
>>> variable. The standard at the time called for X cycles in 12 hours.
>>> You could watch synchronous clocks jump as much as three minutes at
>>> noon as they made up the necessary cycles, Hz today.
>>> Bob Cham
>>>> For what it's worth, in the early 1950's, from 1951 until 1954,
>>>> there were times in Minneapolis and Chicago when my father would
>>>> have to use Fairchild's Pic-Sync system to assure correct
>>>> pitch/speed in his recording truck. The truck's power panel had a
>>>> frequency meter that monitored the power line. He said Minneapolis
>>>> in particular had unreliable power frequency in those days. The
>>>> tradeoff with the Pic-Sync system as originally designed is that
>>>> there's a sharp rolloff above 10kHz, because the Pic-Sync signal is
>>>> at 14kHz. However, using modern methods to lock to and then remove
>>>> the Pic-Sync signal, in tests done by Jamie Howarth and myself, we
>>>> recovered usable audio above 10kHz. There seems to be recorded
>>>> information up to, at and above the 14K frequency, the rolloff
>>>> occurs only in the playback. When the Plangent Process is used to
>>>> lock to either bias or the Pic-Sync signal, the band of the tone is
>>>> very narrow and can be notched out, leaving a lot of audio
>>>> information that would have been sharply rolled off by Fairchild's
>>>> Pic-Sync playback system (resolver) or similar devices. We found
>>>> surprisingly little beating and other interaction with music audio.
>>>> I have to say, the whole thing surprised and impressed me, the
>>>> quality and the frequency range of the audio recovered. I would
>>>> certainly never use an analog Pic-Sync resolver again, for any
>>>> Pic-Sync tape.
>>>> In contrast to the variable Midwest power frequencies in the early
>>>> 50's, another power system story oft-told by my late friend and
>>>> mentor Bob Eberenz concerned Manhattan during hot summers in the
>>>> 60's. While the frequency would be rock-solid 60Hz, the voltage
>>>> could drop as low as 95V in Midtown, overheating the wiring and
>>>> various pieces of equipment. Bob obtained some massive step-up
>>>> transformers, and could thus keep the control rooms running on
>>>> 110-120V under most circumstances. He said the big lines coming
>>>> into the building in the sub-basement would be so hot you could
>>>> pour water on them and it would boil right off.
>>>> -- Tom Fine
>> John Gledhill
>> BIT WORKS Inc.
>> 905 881 2733
>> [log in to unmask]
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