Six Pips On Radio
For 75 years the major global news headlines of the day have been preceded by the six Greenwich Time 'pips'. When the news of Neil Armstrong's first steps on the moon, President John F Kennedy's assassination and the destruction of the Berlin Wall were broadcast across the world on the BBC, they followed the familiar sound of the Greenwich pips.

On the 75th anniversary of the first broadcast of the six-pip Greenwich Time Signal by the BBC, the Royal Observatory displayed for the first time in public, the time pieces which produced the six pips for their first broadcast in 1924. The 1874 Dent regulators have recently returned to Greenwich following the closure of the Royal Greenwich Observatory at Cambridge.

The six-pip Time Signal was introduced following the successful broadcast of the chimes of Big Ben to usher in the New Year of 1924. Late in 1923, Frank Dyson, ninth Astronomer Royal, visited John Reith, Director General of the BBC, to discuss the idea of public time signals being broadcast. The six-pip Time Signal (pips for seconds 55,56,57,58,59,00) was Dyson's brainchild, devised in discussion with Frank Hope-Jones, inventor of the free pendulum clock, who had originally advocated a five-pip signal. The sixth pip signals the start of the next minute.

In 1939, the six pip signal and the Time Service moved from Greenwich to the magnetic observatory at Abinger in Surrey. They then moved to Herstmonceux, Sussex in 1957. In 1990, the Greenwich Time Service transmitted its last pips. Since then the BBC has originated its own pips based on signals from the GPS satellite network and from the 60kHz radio transmitter at Rugby, operated by BT Aeronautical and Maritime under contract to the National Physical Laboratory.

Jonathan Betts, Curator of Horology at the Royal Observatory, said "It is entirely fitting that we display the timepieces which spread GMT and the famous 'pips' across the world at a point in history when time is on everyone's minds. We are pleased to give recognition to the work of Sir Frank Dyson and to commemorate the historic link between the Observatory and the BBC."

The 'six pips' on digital radios

BBC radio has been broadcasting the six-pip time signal since 1924, after setting up a joint venture with the Royal Observatory, Greenwich. The system connected Greenwich timekeeping technology with BBC broadcast technology.

From the start, the pips have proved accurate, reliable and extremely popular with an increasingly-time-bound global audience. But a new technology being introduced to broadcast radio, digital audio broadcasting (DAB), has caused a problem with the accuracy of the time signal.

BBC radio is now broadcast not only for conventional analogue receivers, but also for digital radios, digital televisions and the internet. However, anyone listening on a digital set will have discovered a delay – of several seconds – which means that, whilst the analogue pips remain correct, the digital version cannot be used as an accurate time signal.

The broadcast delay on DAB, while substantial, is relatively predictable, meaning that a fix could be introduced at the transmitter end to broadcast 'early', causing the signal to be received 'on-time'. But a far bigger problem is an additional delay introduced by each radio receiver as it processes the signal.

Unfortunately, that delay varies from model to model – up to seven seconds in the worst case – and it is this receiver delay variation which prevents the BBC from implementing a standard solution. Internet listeners have an even greater problem, with delays being particularly unpredictable on that medium.

Technicians at the BBC have told us how they plan to address the issue. While the problem rests more with receivers than the transmitters, nevertheless they hope to introduce a solution which will fix the problem for 90% of sets (although no date has been given) which would yield pips accurate to about 0.2 seconds for those receivers. But those one-in-ten listeners with receivers outside the norm will not be able to use the pips as an accurate time signal.

Where else can one get accurate time-of-day? An alternative service is the MSF radio signal, a coded message previously broadcast from Rugby, but transmitting from Anthorn , which originates from the atomic clocks in the National Physical Laboratory, the UK's official timekeeper. Clocks and watches which set themselves right according to this radio signal are becoming cheaper and more common.

Alternatively, the British telephone time service, the Accurist 'speaking clock', remains a popular and convenient option as it has done since its inception as 'TIM' in 1936. But listeners to BBC radio who time their lives according to the familiar pips should note that the signal heard on all conventional analogue radios is still as accurate as ever.