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The eccentric engineer: a tale of six pips and how the BBC became the national arbiter of time

Image credit: K. Mitch Hodge | Unsplash

This edition of Eccentric Engineer tells the story of the BBC Time Signal and how, over the years, it has just got more complicated.

Every engineer needs to know the time, if only so as to not miss lunch. Since 1924, many Britons have been checking their watches against the BBC time signal, known affectionately as ‘the pips’.

The history of the ‘pips’ is almost as long as the history of the BBC itself. The first transmissions from what was then the British Broadcasting Company began in late 1922 and soon afterwards there were suggestions of broadcasting a time signal under the control of the Royal Observatory at Greenwich – then the arbiter of time in the UK.

No one seems to have seen a need for this degree of precision, but early broadcasts did use their own ad hoc ‘pips’, marking the 8pm and 9pm news programmes with a time signal consisting of the announcer playing the Westminster chimes on a piano and later a set of tubular bells. This proved rather popular with listeners, who could now adjust their clocks and watches daily, so the BBC decided to invest in some more high-tech clocks from the Synchronome Company. These provided audible ‘ticks’, which the announcer then simply counted down.

The idea for the actual pips probably came from amateur horologist and radio enthusiast Frank Hope-Jones, who ended a particularly well-timed radio lecture by counting down the last five seconds to 10pm. After this, he suggested that the BBC might broadcast an audible time signal.

John Reith, managing director of the BBC, decided to contact the Astronomer Royal, Frank Watson Dyson, to discuss the idea. Dyson agreed to modify two clocks at Greenwich, so their escapement wheels controlled a switch on a 1kHz oscillator, which sent this signal down a telephone line to the BBC to produce a time signal every half-hour. To help people set their watches it was decided to broadcast six tones from the oscillator starting at five seconds to the hour and ending on the hour, the start of the last tone being the hour itself. The ‘pips’ were first transmitted at 9.30pm on 5 February 1924, introduced by Dyson himself.

For 13 years the system worked well, until the Royal Navy, which controlled Greenwich Observatory, realised the BBC had never paid for the service and sent them a bill. In return, the BBC reminded the Navy that they had never billed them for the shipping forecast and the matter of fees was quietly dropped.

When the Royal Observatory moved to Herstmonceux Castle in Sussex in 1958, the ‘pips’ had to move, too. Here, two electric clocks generated the signal, which was sent down two phone lines (one for redundancy) to the BBC in London. To confirm that the lines were working the clocks sent a continuous tone all the time, the ‘pips’ being short silences. This signal was turned into 1kHz ‘pips’ by the BBC.

With the occasional spurious pip, the time signal survived largely unchanged until 1971, when an international agreement brought all time signals on to International Atomic Time (IAT). While this hardly bothered those setting their watches before the news, it bothered the timekeepers. IAT is relentlessly accurate whereas the Earth itself is not, running slightly slow. It was decided that local time, such as GMT, would have to occasionally be adjusted by adding a ‘leap second’. Yet this proved problematic for the ‘pips’. Obviously, a seventh ‘pip’ could be added, but how would the audience know which was the last pip? The answer was to alter the length of the last pip from 0.1s to 0.5s and so the familiar sounding last ‘pip’ was born.

From 1990, the BBC took over creating the signal itself, always aiming at higher accuracy and even adjusting for the time it takes the signal to travel to the transmitter and then to the receivers, even though these fractions of seconds are far less than the time lost in the sound getting from the radio to the listeners’ ears. Of course, occasionally things went wrong. At 8am on 17 September 2008, seven ‘pips’ were broadcast six seconds late. To this day, no one knows why, but the machine was reset by switching it off and on again and has worked well ever since.

Being a story of scientific endeavour, one might expect that from here on in, it just gets more accurate – but you’d be wrong. With the advent of digital radio and internet, the time signal has become, ironically, far less accurate. Digital signals need to be encoded and decoded and for digital radio this can take 1.5 seconds. For the BBC website, it can be as long as 10 seconds. The digital age may herald the end of the ‘pips’ as we know them. Time to dust off those tubular bells.

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