A fun tidbit about crystal oscillators is that they allowed “un-tethered” sound recording on motion picture film cameras. If both your sound recorder and your film camera are using a crystal oscillator as a reference for their motors - you can sync them up in post without needing them to be physically connected during filming.

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tverbeure 2 days ago | parent [-]

I imagine that the accuracy requirements for those crystals are not quite as stringent as the one that I’m talking about here!

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dn3500 a day ago | parent [-]

An entire 1000 foot reel of 35 mm film only has about 15,000 frames on it, so one part in 30,000 would be good enough. When I worked in TV none of the sound equipment had ovens for their crystals.

We did have a sync generator with a crystal oven. I forget who made it. The sync generator has multiple outputs, the most important one being the color subcarrier, which is 3.579545 MHz for US NTSC (I still remember that number). It also puts out vertical and horizontal sweep signals. The stable timebase allowed us to free run for a day in case we lost the network signal for some reason. The network (NBC in our case) had a cesium clock in New York that they calibrated against WWV for time of day. We locked our clock to their signal, and all our equipment to our clock.

	▲	tverbeure 17 hours ago \| parent [-]
		As a teenager, I was fascinated by live video effects and mixing multiple video streams. And I assumed that the TV station had equipment with huge amount of storage (this was in the eighties) and sync streams together. During a visit at the Belgian national broadcast corporation, they showed the central clock generator to which all video sources were synced. It suddenly all made sense. :-)