Atomic clock devices are expensive pieces of equipment mainly confined to national laboratories. However, there are a number of atomic clock references available free to air for computer time synchronisation.
The DCF-77 atomic clock radio signal is broadcast from Frankfurt in Germany. The time signal is broadcast at 77.5 kHz. Coverage is most of central and north-western Europe.
The radio signal is broadcast as a sequence of 60 pulses, one pulse per second, each pulse constitutes a data bit. A minutes worth of data bits encode the time and date information. The data string is terminated on the minute boundary by a marker to signify the start of a minute.
TimeTools NTP time Servers and Radio based time servers have DCF-77 reception options.
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