This is sufficient for radio controlled low cost consumer grade clocks and watches using standard-quality quartz clocks for timekeeping between daily DCF77 synchronization attempts, as they will be most accurate immediately after a successful synchronization and will become less accurate from that point forward until the next synchronization. Some DCF77 controlled consumer grade quartz movements promote accurate time keeping by synchronizing and correcting their time automatically more than once spread over a day. Network Time Protocol reference clock use Network Time Protocol time servers display the refid identifier .DCFa. (amplitude modulation) or .DCFp. (phase modulation) when a standard DCF77 time receiver is used as the reference time source. References Further reading (4 pages) External links Official DCF77 web page at the PTB The atomic clock in Frankfurt/Main Germany DCF77 on the Global Frequency Database Time code description Observation of DCF77 during a leap second DCF77 Arduino implementation Hardware, Signal, Code Meteotime Time and frequency dissemination with DCF77: 1959–2009 and beyond" – a detailed description of the history of DCF77 How to build a clock DCF (archive.org copy) A historical visit at DCF77 Mainflingen by Ekkehard Plicht Time signal radio stations Time in Germany Transmitter sites in Germany Call signs 1959 establishments in West Germany