A clock at the US Naval Observatory supplied time for the first radio broadcast time signals in 1903. This experiment was soon followed by regular broadcasts from many countries as an aid for navigators at sea. The Bureau International de l'Heure (BIH, International Time Bureau) was chartered in order to receive radio broadcasts of time signals and intercompare them.
The USNO was one of several other agencies which intercompared
broadcasts from many sites with clocks set by many
observatories.
Starting in 1953 the USNO published the results of the
intercomparisons in a long-running series of Time Signals
Bulletins.
Bulletin A originally gave final times of reception at
Washington.
Starting with the issue for signals in 1960 Bulletin A gave
final times of emission.
Bulletin B was the more rapid publication and originally gave
preliminary times of reception (subject to revision) at
Washington.
Bulletin B later added estimated deviations of frequency.
Starting with the issue for signals in 1960 Bulletin B gave
preliminary times of emission.
Bulletin A and B were combined into a single publication with
the issue for radio signals from the beginning of 1961.
The combined Bulletin originally included differences at time of
emission from UT2 and from Atomic Time, and also the PZT
observations of time at the USNO stations in Washington DC and
Richmond Florida.
The USNO published a series of Time Service Announcements. These announcements gave advance warning of changes in frequencies, times of day during which broadcasts were made, locations of transmitters, and intervals when broadcasts would be down for maintenance and upgrades. This was important for ships and aircraft which relied on these signals these signals for real-time navigation. Changes to the time being broadcast had to be announced and explained in advance so that the users could prepare changes in their procedures and calculations that made use of the time signals.
One set of the Time Service Announcements provides insight into the decision making processes and priorities that led to the inception of leap seconds.
The USNO also published a series of Time Service Notices. The notices gave explanations about the characteristics of time scales and technologies used for time and frequency.