how do digital devices (like phones, computers) keep time? I get clockwork but even my fairy lights have a timer on – how?
In: Technology
The simple way to have an accurate close in an electrical unit is with a crystal oscillator.
It is a physical crystal that is shaped so it vibrates at a specific frequency just like how a tuning fork vibrates a specific frequency. Some of them are [fork-shaped](https://en.wikipedia.org/wiki/Tuning_fork#/media/File:Inside_QuartzCrystal-Tuningfork.jpg) and for clocks, they are tuned to 32768 Hz.
They can be used to create an electrical signal with just that frequency and you then have a circuit that counts the pulses to measure time. after you count 32768 pulses a second have passed.
There is a reason that you have mechanical clocks and quartz clock.
When in operation you have a crystal with a higher frequency that produces the color signal that the device uses internally. But when turned off you have a small battery, crystal, and part of a chip just to run the clock all the time.
Any net-connected device can use a standard protocol to connect to a time server to get the exact time so your phone and computer will get and update the time multiple times per day if you leave the function enabled.
Clock chips are cheap and the feature might increase fairy-light sales.
Phones get their time from the cellular network. The cellular network in turn gets its time from GPS satellites. GPS satellites get their time from the reference clocks like the atomic clock at the US Naval Observatory (there are a few other reference clocks around the world). The GPS satellites themselves also have atomic clocks on board. GPS time is about as close to “real” time as you can get without being connected directly to the reference clocks.
Computers have a protocol called NTP – Network Time Protocol. NTP is handled in “stratums” or layers. A “stratum 0” server is one of the aforementioned reference clocks or a GPS satellite. A “stratum 1” server is a server that is time synced to a stratum 0 server. I used to have a stratum 1 time server at home because my local server was connected to a GPS receiver that outputted time signals. Then all the computers in the house could time sync off that server. As it stands right now, Microsoft runs some time sync servers as does Apple so their operating systems can sync off those.
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