Time signal (tone sequence)
A time signal is a distinctive sequence of tones that signals a specific time in a radio program , for example every hour on the hour or the start of a news broadcast, often with a preliminary identifier. Film excerpt from 4 min. 15 sec. It usually consists of five short tones on the last seconds before the full hour or half an hour, followed by a different (e.g. longer, lower or higher) tone exactly to the second zero (e.g. the beginning of the hour).
This service was later also taken over by the television broadcasters , which, however, only faded in a clock at the beginning of their news programs and not every full hour and broadcast a corresponding sequence of tones as on the radio.
In earlier times, these time signals were used by listeners to compare time in order to set their mechanical clocks precisely. Today this is no longer possible because the digitized studio technology and the digital transmission paths to the transmitters and from the transmitters to the receiver (e.g. via DAB ) result in an indefinable time delay which no longer guarantees the required accuracy of the second. This service gradually became superfluous anyway, because many clocks are automatically synchronized, mostly by radio long-wave time signals, for example from DCF77 . The time information from the RDS , teletext or EPG data is also no longer accurate to the second due to the delay, but is used to synchronize the device's own clocks and comes from the radio station itself.
In some countries (e.g. Italy, Spain, Eastern Europe) it was and is still customary to send a time signal on the hour, even if there is no news broadcast. The time signal then occurs either in the background of the current broadcast or in a short pause. This practice still partially exists today at RAI in Italy or at Catalunya Ràdio in Catalonia. On some channels there are or were time signals at half an hour.
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