alt Hacker NewsIn [3] he mentions that one can use NTP to observe frequency deviations and use it as an early warning system for fire and AC failure. That really intrigues me. Can you actually? Has this ever been implemented?
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I knew of some experiments in this space back in the late 1980s or early 1990s - but it was specifically with DECstation hardware that had terrible clocks (not used for alerting, just "this graphs nicely against temperature".) https://groups.csail.mit.edu/ana/Publications/PubPDFs/Greg.T... (PDF) 4.2.1 does talk about explaining local clock frequency changes with office temperature changes (because they overwhelm a clock-aging model) but it doesn't have graphs so perhaps they weren't clear enough to include (or just not relevant enough to Time Surveying.)
Oscillators of all kinds are temperature dependent.
That's why the most stable ones are insulated and ovenized[1].
So an AC failure which would lead to higher room temperatures would lead to stronger or more frequent correction by the NTP client, as the local oscillator would drift more.
Not sure about the fire case though. I mean the same applies there but I'm not imaginative enough to think of a realistic scenario where NTP would be useful for averting a fire.
[1]: https://blog.bliley.com/anatomy-of-an-ocxo-oven-controlled-c...