A Step in Time: Changes in Standard-frequency and Time-signal Broadcasts -- January 1, 1972
An improved coordinated universal time (UTC) system has been adopted by the International Radio Consultative Committee. It was implemented internationally by the standard-frequency and time-broadcast stations on 1 Jan. 1972. The new UTC system eliminates the frequency offset of 300 parts in 10 to the 10th power between the old UTC and atomic time, thus making the broadcast time interval (the UTC second) constant and defined by the resonant frequency of cesium atoms. The new time scale is kept in synchronism with the rotation of the Earth within plus or minus 0.7 s by step-time adjustments of exactly 1 s, when needed. A time code has been added to the disseminated time signals to permit universal time to be obtained from the broadcasts to the nearest 0.1 s for users requiring such precision. The texts of the International Radio Consultative Committee recommendation and report to implement the new UTC system are given. The coding formats used by various standard time broadcast services to transmit the difference between the universal time (UT1) and the UTC are also given. For users' convenience, worldwide primary VLF and HF transmissions stations, frequencies, and schedules of time emissions are also included. Actual time-step adjustments made by various stations on 1 Jan. 1972, are provided for future reference.
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24h in winter 30 June adopted Al-type second pulsesd astronomical atomic clock atomic standards BIH announced BIH Annual Report BIH Circular Bureau of Standards CCIR code is given coordinated universal crystal clocks cycles D3—Foreign radio station DUT1 code information dUTl emphasized seconds markers Frequency kHz given by lengthening given in Appendix improved UTC system Interim Meeting International de l'Heure International Telecommunication Union January minute marker minute pulses minutes 15 modulation Morse code N.long National Bureau negative leap second Observatoire de Paris Physikalisch-Technische Bundesanstalt positive leap second preceding the indicated pulses are prolonged pulsesd are emitted Radio Consultative Committee Recommendation 460 Republic of Germany rotation Second pulses occur seconds markers Service Announcements standard-frequency and time-signal step step-time adjustments Study Group Table D3—Foreign radio Telecommunication time-signal emissions timekeeping U.S. Naval Observatory users USNO value of DUT1 worldwide primary VLF WWVB WWVH