Greenwich Time Signal

The Greenwich Time Signal (GTS), popularly known as the pips, is a series of six short tones (or "pips") broadcast at one-second intervals by many BBC Radio stations. The pips were introduced in 1924 and have been generated by the BBC since 1990 to mark the precise start of each hour. Their utility in calibration is diminishing as digital broadcasting entails time lags.

Structure

There are six pips (short beeps) in total, which occur on each of the 5 seconds leading up to the hour and on the hour itself. Each pip is a 1 k Hz tone (about a fifth of a semitone above musical B5) the first five of which last a tenth of a second each, while the final pip lasts half a second. The actual moment when the hour changes – the "on-time marker" – is at the very beginning of the last pip.

When a leap second occurs (exactly one second before midnight UTC), it is indicated by a seventh pip. In this case the first pip occurs at 23:59:55 (as usual) and there is a sixth short pip at 23:59:60 (the leap second) followed by the long pip at 00:00:00. The possibility of an extra pip for the leap second thus justifies the final pip being longer than the others, so that it is always clear which pip is on the hour. Before leap seconds were conceived, the final pip was the same length as the others. Although "negative" leap seconds can also be used to make the year shorter, this has never happened in practice.

Although normally broadcast only on the hour by BBC domestic radio, BBC World Service uses the signal at other times as well. The signal is generated at each quarter-hour and has on occasion been broadcast in error.

Until 1972, the pips were of equal length and confusion arose as to which was the final pip, hence the last pip is now of extended length.

Usage

The pips are available to BBC radio stations every fifteen minutes, but, except in rare cases, they are only broadcast on the hour, usually before news bulletins or news programmes. Normally, BBC Radio 4 broadcast the pips every hour except at 18:00 and 00:00, and at 22:00 on Sundays (at the start of the Westminster Hour) when they are replaced by the striking of Big Ben at the Palace of Westminster. No time signal is broadcast at 10:00 on Sundays, before the omnibus edition of ''The Archers''. On BBC Radio 2, the pips are used at 07:00, 08:00 and 17:00 on weekdays, at 07:00 and 08:00 on Saturdays and at 08:00 and 09:00 on Sundays.

The pips were used on BBC Radio 1 during ''The Chris Moyles Show'' at 06:30 just after the news, 09:00 as part of the "Tedious Link" feature, 10:00 (at the end of the show) and often before ''Newsbeat''. As most stations only air the pips on the hour, ''The Chris Moyles Show'' was the only show where the pips were broadcast on the half-hour. Chris Moyles continues to use the pips at the beginning of his show on Radio X. The pips were previously used at 19:00 on Saturday evenings at the start of Radio 1's 12-hour simulcast with digital station BBC Radio 1Xtra. On 19 September 2022 on Radio 4, A 10 minute long pip was used at 10:50 before The Queen's
State funeral began at 11:00 BST. The pips were also used on Radio 6 Music for a rare occurrence. It took place between 2009 and 2011 on weekdays and the pips were played at 10:00 (end of the breakfast show) and at 19:00 (end of the drive show). On Remembrance Day and Remembrance Sunday, Radio 4 uses the pips at 10:59:55 to mark the start of the two minutes silence and again at 11:01:55 to mark the end. From 2000 to 2008. BBC Radio 5 live used the pips Weekdays at 06:00

BBC Radio 3 and BBC Radio 5 Live do not currently broadcast the pips.

The BBC World Service broadcasts the pips every hour.

Pips were also heard on many BBC Local Radio stations until the introduction of a new presentation package in 2020. A rare quarter-hour Greenwich Time Signal was heard at 05:15 weekdays on Wally Webb's programme on local radio in the east of England until it ended in March 2020, as part of his "synchronised cup of tea" feature.

In 1999, pip-like sounds were incorporated into the themes written by composer David Lowe to introduce BBC Television News programmes. They are still used today on BBC One, BBC Two, BBC World News and BBC News.

The BBC does not allow the pips to be broadcast except as a time signal. Radio plays and comedies which have fictional news programmes use various methods to avoid playing the full six pips, ranging from simply fading in the pips to a version played on '' On the Hour'' in which the sound was made into a small tune between the pips. ''The News Quiz'' also featured a special Christmas pantomime edition where the pips went "missing", and the problem was avoided there by only playing individual pips. The 2012 project ''Radio Reunited'' used the pips to commemorate 90 years of BBC Radio.

Accuracy

The pips for national radio stations and some local radio stations are timed relative to UTC, from an atomic clock in the basement of Broadcasting House synchronised with the National Physical Laboratory's Time from NPL and GPS. On other stations, the pips are generated locally from a GPS-synchronised clock.

The BBC compensates for the time delay in both broadcasting and receiving equipment, as well as the time for the actual transmission. The pips are timed so that they are accurately received on long wave as far as from the Droitwich AM transmitter, which is the distance to Central London.

As a pre- IRIG and pre- NTP time transfer and transmission system, the pips have been a great technological success. In modern times, however, time can be transferred to systems with CPUs and operating systems by using BCD or some Unix Time variant.

Newer digital broadcasting methods have introduced even greater problems for the accuracy of use of the pips. On digital platforms such as DVB, DAB, satellite and the Internet, the pips—although ''generated'' accurately—are not ''heard'' by the listener exactly on the hour. The encoding and decoding of the digital signal causes a delay, of usually between 2 and 8 seconds. In the case of satellite broadcasting, the travel time of the signal to and from the satellite adds about another 0.25 seconds.

History

The pips have been broadcast daily since 5 February 1924,
and were the idea of the Astronomer Royal, Sir Frank Watson Dyson, and the head of the BBC, John Reith. The pips were originally controlled by two mechanical clocks located in the Royal Greenwich Observatory that had electrical contacts attached to their pendula. Two clocks were used in case of a breakdown of one. These sent a signal each second to the BBC, which converted them to the audible oscillatory tone broadcast.

The Royal Greenwich Observatory moved to Herstmonceux Castle in 1957 and the GTS equipment followed a few years later in the form of an electronic clock. Reliability was improved by renting two lines for the service between Herstmonceux and the BBC, with a changeover between the two at Broadcasting House if the main line became disconnected.

The tone sent on the lines was inverted: the signal sent to the BBC was a steady 1 kHz tone when no pip was required, and no tone when a pip should be sounded. This let faults on the line be detected immediately by automated monitoring for loss of audio.

The Greenwich Time Signal was the first sound heard in the handover to the London 2012 Olympics during the Beijing 2008 Olympics closing ceremony.

The pips were also broadcast by the BBC Television Service, but this practice was discontinued by the 1960s.

To celebrate the 90th birthday of the pips on 5 February 2014, the ''Today'' programme broadcast a sequence that included a re-working of the Happy Birthday melody using the GTS as its base sound.

Crashing the pips

The BBC
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