Quote:
Originally Posted by broadgage
In years gone by, cinema projectors were tied to the line frequency, and cinema staff with a good watch or clock could just about detect that the actual running time of a film could vary by a minute or so.
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Only approximately. Often, induction motors were used, and these have 'slip' so only loosely tied. And the projector mechanism may be belt-driven too, another opportunity for slip.
However, assuming these are constant, yes a small frequency change in the mains could still manifest itself in a minute or so variation in duration.
I recall Adrian Hope (Barry Fox) in an article, pointing out that crystal-locked turntable motors might actually be unnecessarily more accurate than the records they would be playing, as recording lathes were driven by off-line AC motors so could vary by the supply frequency.
Quote:
Originally Posted by Andrew2
...we must all bear in mind that God invented time to prevent everything happening at once!
Who was it that said that?
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Dunno! But He did a good job, time (or frequency) is the quantity which we've been able to measure with the best precision of anything!