Greenwich Time Signal: Map

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Graph of the six pips

The Greenwich Time Signal (GTS), popularly known as the pips, is a series of six short tones broadcast at one-second intervals by many BBC Radio stations to mark the precise start of each hour. First introduced in 1924, the viability of continued use of the time signal on radio is under discussion , as the unavoidable time lags associated with digital broadcasting systems make its use less feasible as an aid to calibration.

Structure

There are six pips (short beeps) in total, which occur on the 5 seconds leading up to the hour and on the hour itself. Each pip is a 1 k Hz tone (about half way between musical B5 and C6), which, for the five, last each a tenth of a second, 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), 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 leap second is also the explanation for the final pip being longer than the others. This is so that it is always clear which pip is on the hour, especially where there is an extra pip that some people might not be expecting. Before leap seconds were conceived the final pip was the same length as the others. Leap seconds can also be used to make the year shorter, but in practice this has never happened.

Although normally broadcast only on the hour, the signal is also generated, with fewer pips, at each quarter hour. These are occasionally broadcast in error at these times, though they are equally accurate so no harm is done beyond the interruption.

Usage

The pips are used by several stations on some, or every, hour. On Radio 4, the pips are replaced at the start of the 6pm and midnight news bulletins (and on Sundays at 10pm) by the Westminster chimes from the Clock Tower at the Palace of Westminster

, with the hour chimes of Big Ben

, sometimes called the "bongs" (though these are more associated in the popular mind with ITV's News at Ten).

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 World News and BBC News. The pips can also be heard every hour on the BBC's worldwide radio station BBC World Service.

The pips are used on Radio 1: on The Chris Moyles Show at 6.30am just after the news, 9am as part of the Tedious Link feature, 10am (at the end of the show), and sometimes before Newsbeat bulletins. Masterpieces, the playing of an album in its entirety, is begun with pips, and they also feature at 7pm on Fridays to signify the weekend.

The pips are used on Radio 2 at 7am (during Sarah Kennedy's show), 8am (during Terry Wogan's breakfast show) and at 5pm (between Steve Wright's and Chris Evans show), Zoe Ball's show at 7am and 8am on a Saturday and at 8am and 9am on a Sunday during Aled Jones' show.

The pips are used on 5 Live at 12:30am in the early hours of Tuesday to Friday to signify the start of the Special Half Hour segment on Richard Bacon's late evening show.

Broadcasting the pips is frowned on by the BBC except as a time signal. 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.

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— the speed of light being pretty much irrelevant for these purposes (and, in any case, unavoidable).

Newer digital broadcasting methods have introduced even greater problems for the accuracy of use of the pips. On digital platforms such as DVB, DAB and the Internet, the pips — although generated accurately — are not received by the listener exactly on the hour. The encoding and decoding of the digital signal causes a delay, 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 machine used to generate the pips in 1970

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. 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

should the main line become disconnected.

The tone sent on the lines was inverted: the signal sent to the BBC was a steady electric current when no pip was required, and no current when a pip should be sounded. This let faults on the line to be detected immediately by continuous loss of current.

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 although this practice had been phased out by the 1960s.

Crashing the pips

It is frowned upon at the BBC to talk, play music or otherwise make noise while the pips sound, and doing so is commonly known as crashing the pips. This is most often referred to on Wogan's show, although usually only in jest since the actual event happens rarely.

As a contribution to the 2005 Red Nose Day, the BBC developed a "pips" ring-tone.On the 2009 Red Nose Day, well-known comedians replaced the continuity announcers for most of the daytime output of Radio 4, and it seems deliberately crashed the pips— the first crash by Jo Brand was perhaps a genuine mistake, but as the day progressed every other announcer did the same.

Bill Bailey's self styled comedy included the BBC Rave, which includes the BBC News theme, which incorporates a variant of the pips (though not actually broadcast exactly on the hour). The footage can be seen on his DVD Part Troll.

In the late 1980s, Radio 1 featured the pips played over a station jingle during Jakki Brambles' early show and Simon Mayo's breakfast show. This was not strictly crashing the pips as they were not intended, or mistaken for, an accurate time signal.

At 8am on 17 September 2008, to the surprise of John Humphrys, the day's main presenter on the Today programme and Johhnie Walker who was standing in for Terry Wogan on Radio 2, the pips went adrift by 6 seconds, and broadcast seven pips rather than six. This was traced to a problem with the pip generator, which was 'repaired' by switching it off and on again. Part of Humphrys' surprise was probably because of his deliberate avoidance of crashing the pips; an accurate clock in the studio helps presenters keep time.