you can get this also via the Internet (as an NTP service) to synchronise your computers (I need accurate time for both work and monitoring the radio stations) but I also use a standalone receiver as a double check in case there are network problems (lag and jitter delays the time signal).
This is a demonstration of how the signal (transmitted on a low frequency of 60 Khz, just above audio) works – and what it sounds like if received on USB mode (like what is used to decode morse code).
Note how the signal changes at the first second of a new minute, and the double pips (these are a binary code containing the date and other info like whether we are on GMT or BST)
its an enhancement of an old-skool time signal orignally sent by the British Post Office but with digital encoding and error correction. A standalone receiver can check the time every minute (if the signal isn’t being swamped by interference), whereas most computer clients will do only every 10 minutes (NPL also don’t like it if you repeatedly cane their server).
Computers are surprisingly bad at telling time – Even within 15 minutes this machine (a fairly powerful x64 machine with 8 gigs) drifted 451ms. So if they aren’t properly synchronised a PC can be wrong by several seconds within a few days, worse than a cheap china wristwatch. A second is a long period of time in broadcasting and telecommunications, especially if the signal you expected to be there isn’t present or mistimed!
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