Greenwich Time Signal

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. 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 the 5 seconds leading up to the hour and on the hour itself. Each pip is a 1 kHz tone (about half way between musical B5 and C6), which, for the first five, last 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. "Negative" 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 by BBC domestic radio, BBC World Service use the signal at other times as well. The signal is generated at each quarter hour and has on occasion been broadcast in error.

Usage

The pips are used by several stations, but not always at every hour. On Radio 4, the pips broadcast every hour, except when they are replaced at the start of the 6pm and midnight news bulletins (and the start of the Westminster Hour 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 during 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 often before Newsbeat. As most stations only air the pips on the hour, the Chris Moyles show is the only show where the pips are broadcast on the half hour. Masterpieces, the playing of an album in its entirety, is begun with pips, and they also feature at 7pm on Fridays to signify the start of the weekend and at 4pm on Sundays to mark the start of The Official Chart Show. The pips are also used at 7pm on Saturday evenings at the start of Radio 1's 12-hour simulcast with digital station BBC Radio 1Xtra.

The pips are used on Radio 2 at 7am and 8am during The Chris Evans Breakfast Show and at 5pm between Steve Wright's and Simon Mayo's show. They are also broadcast during Zoë Ball's show at 7am and 8am on a Saturday and at 8am and 9am on a Sunday during Aled Jones' show. Radio 2's coverage of the Eurovision Song Contest is preceded by the pips.

The pips were 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.

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.

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 160 kilometres (100 mi) 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.

DVB, DAB (Eureka 147 and Digital Radio Mondiale) and FM Radio Data System all support separate time signal transmission subsystems with accuracy equal to or several orders of magnitude better than the pips, so the listener need not worry about decoding the pips to synchronize the clocks on these systems.

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 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 become 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.

Crashing the pips

The BBC discourages any other sound being broadcast at the same time as the pips; doing so is commonly known as 'crashing the pips'. This was most often referred to on Terry Wogan's show, Wake Up to Wogan, although usually only in jest since the actual event happens rarely. Different BBC Radio stations approach this issue differently. BBC Radio 1 has a more laid-back approach with the pips, the most notable example being The Chris Moyles Show which usually plays the pips over a currently playing song or a jingle 'bed' (background music from a jingle) which climaxes into the jingle after the pips end. Many BBC local radio stations also play the pips over the station's jingle. BBC Radio 4 is stricter. It is an almost entirely speech-based network; incidents at the end of the Today programme regularly cause listeners' complaints.

As a contribution to the 2005 Red Nose Day, the BBC developed a "pips" ring-tone.

Bill Bailey's BBC Rave 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 to be, or mistaken for, an accurate time signal.

Technical problems

At 8am on 17 September 2008, to the surprise of John Humphrys, the day's main presenter on the Today programme, and Johnnie 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 with the help of an accurate clock in the studio.

A sudden total failure in the generation of the audio pulses that constitute the pips was experienced on 31 May 2011 and silence was unexpectedly broadcast in place of the 17:00 signal. The problem was traced to the power supply of the equipment which converts the signal from the atomic clocks into an audible signal. Whilst repairs were underway the BBC elected to broadcast a "dignified silence" in place of the pips at 19:00. By 19:45 the same day the power supply was repaired and the 20:00 pips were broadcast as normal.

Similar time signals elsewhere

Many radio broadcasters around the world use the Greenwich Time Signal as a means to mark the start of the hour. The pips are both used in domestic and international commercial and public broadcasting. Many radio stations use six tones similar to those used by the BBC World Service; some shorten it to five, four, or three tones.

In Australia, pips are used on ABC Radio National and ABC Local Radio at the top of every hour.

In Hong Kong pips are used on RTHK's radio channels for the same purpose and in the same way. The signals, which are provided by the Hong Kong Observatory, are broadcast every half hour during the day and on the hour at night, immediately before the news headline reports.

In Finland on YLE's radio services the pips are broadcast on the hour.

In The Netherlands only three pips are used. There used to be six, however it was felt that people would lose count, so now only three are used.

In Spain, the signal is broadcasted by almost all radio stations, even by music stations, but depends on them the frecuency: music ones usually use pips on the hour, but most of non-musical radios broadcast the signal every 30 minutes. Los 40 Principales, the most important music radio in Spain, broadcast a different version of GTS: two first pips sound and then a music is added on the background, using the rhythm to create the corporative jingle of the radio. Other musical radios like Máxima FM and M80 Radio, both owned by PRISA, and Europa FM use a similar effect.

In Catalonia, dance music station Flaix FM and Hot AC station Ràdio Flaixbac, both owned by the same media group, broadcast every half hour a very short sequence of two very short tones followed by a longer one, the whole lasting not more than one and a half seconds. Els 40 Principals, the catalan edition of spanish radio Los 40 Principales, use the same jingle, using a mix of GTS and corporative music.

In Malaysia, RTM radio stations use the pips hourly before the news broadcast but only two pips are sounded, which is a short pip on the 59th second before the hour and a longer pip on the top of the hour. In the past, the pips were used to sound similar to the BBC's.

In Ireland, six pips are broadcast before news bulletins at 07:00, 13:00 and 24:00 on RTÉ Radio 1.

In the United States, the pips can be heard on the Middlebury College radio station WRMC.

In North Korea, the pips are heard on Voice of Korea before its startup at 17:00.

Radio New Zealand National, the New Zealand equivalent of BBC Radio 4, plays the same BBC pips at the top of every hour.

See also

• MSF time signal
• National Research Council Time Signal - A CBC Radio One indicator for 1300 ET

External links

• http://www.miketodd.net/other/gts.htm
• http://www.radionetherlands.nl/features/media/practical/time.html
• http://www.clockco.co.uk/article_info.php?articles_id=15