Standard time and frequency signal service
The Standard Time and Frequency Signal (STFS) is a time signal service available in the United States which provides standard time and frequency signals, broadcast on very precise carrier frequencies by the U.S. Naval Observatory and the National Institute of Standards and Technology (NIST), formerly the National Bureau of Standards (NBS).
A similar service is operated in the United Kingdom by the National Physical Laboratory, broadcasting from Anthorn radio station in north-west England, and by the BBC using the 198kHz carrier of the Radio 4 national radio station with a frequency accuracy of 1 part in 1011.
The National Physical Laboratory, India is the premier research laboratory in India in the field of physical sciences. NPLI continues to disseminate standard time and frequency signals (STFS) via geostationary satellite INSAT with an accuracy of 10 ms.
References
This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C".