A century ago the first time signal was transmitted from the historic British observatory in Greenwich to the BBC studios, where it was translated into a succession of six beeps.
It was February 5, 1924 and since then that signal continued to mark time for decades, but then had to give in to the arrival of digital.
The idea for the time signal came from the then director of the British Royal Observatory, astronomer Frank Watson Dyson, and the then head of the BBC, John Reith.
At the time, Greenwich was already an international reference point for the measurement of time: in 1884 the International Meridian Conference had nominated the meridian that passes through the dome of the Greenwich observatory as the fundamental meridian for determining the longitude of each point of the Earth's surface and Greenwich meridian time was the reference for determining the time of events that occurred in different places.
The signal was generated by two mechanical clocks located in the observatory, on whose pendulum electrical contacts had been installed, and which every second sent a signal to the BBC, which transformed them into an audible signal.
Using two clocks was redundant, but necessary to ensure continuity of service if one of them failed.
When the headquarters of the Greenwich observatory was moved to Herstmonceux Castle in 1957, the instrumentation was replaced by an electronic clock, connected to the BBC via two lines.
The move to Cambridge in 1990, with the introduction of a computerized system linked to atomic clocks, was also linked to a technical innovation.
Another change was introduced in 1972, when it was decided to lengthen the duration of the sixth beep.
However, it was the arrival of digital that brought about a radical transformation.
In Italy the Greenwich time signal was broadcast by the RAI radio and television networks, supplied from the early 1940s by the Galileo Ferraris Institute, later merged into the National Institute for Metrology Research (Inrim).
On dedicated lines, the time signals were sent to the Rai headquarters in Turin.
"We began to transmit a time reference signal via radio, based on quartz clocks," says Davide Calonico, of Inrim.
"In the 1970s, the transmission of the Rai time signal consolidated, and from then on it was broadcast by Inrim until 2016.
"Then there was a technological leap and with the transition to digital platforms the analogue signal was delayed. At 8.00 pm on 31 December 2016 the Rai Codified Time Signal was therefore broadcast for the last time from the Rai headquarters in Turin ( Src). "Since then the technology has moved forward and since the mid-2000s it has been based on satellite navigation systems or optical fibre", observes the expert. Today the reference has become the Precision Time Protocol, the protocol used to synchronize computers and mobile phones. "Consequently - concludes Calonico - today anyone with a mobile phone has an accurate time receiver in their pocket".
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