Greenwich Time Signal





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 halfway between musical B5 and C6) 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 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 available to BBC radio stations every 15 minutes but except in rare cases, they are only broadcast on the hour, usually before news bulletins or news programmes. On BBC Radio 4, the pips are broadcast 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 Westminster chimes of Big Ben at the Palace of Westminster. No time signal is broadcast at 15:00 on Saturdays and at 10:00 and 11:00 on Sundays. This is caused by the scheduling of the afternoon play on Saturday and the omnibus edition of The Archers on Sunday. On BBC Radio 2, the pips are used at 07:00, 08:00, 17:00 and 19:00 on weekdays, at 07:00 and 08:00 on Saturdays and at 08:00 and 09:00 on Sundays.

The pips were used on Radio 1 during The Chris Moyles Show at 06:30 just after the news, 09:00 as part of the Tedious Link feature, 10 am (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. Zane Lowe's Masterpieces, the playing of an album in its entirety, is begun with pips, and they also feature at 19:00 on Fridays to signify the start of the weekend and at 16:00 on Sundays to mark the start of The Official Chart Show. The Weekend Breakfast Show with Dev begins with the pips at 06:00, and they sometimes feature on the hour at other points during the show, and Gemma Cairney's Early Breakfast Show begins with the pips. Dev's previous Early Breakfast Show also featured the pips at the beginning, and on the half-hour/hour at other points, particularly at 06:00 before or after the "I'm Here All Week" track. The pips are also used at 19:00 on Saturday evenings at the start of Radio 1's 12-hour simulcast with digital station BBC Radio 1Xtra.

BBC Radio 3 and BBC Radio Five Live do not currently feature the Greenwich Time Signal in their scheduled programming.

The BBC World Service broadcasts the pips every hour.

Pips can also be heard on many BBC Local Radio stations although their use is up to the discretion of individual stations. A rare quarter-hour Greenwich Time Signal can be heard at 05:15 weekdays on Wally Webb's programme on six BBC Local Radio stations in the east of England, as part of his "sychronised 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 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 and not the whole set. The 2012 project Radio Reunited, however, did use the pips not as a time signal, but simply 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 160 km 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&mdash;although generated accurately&mdash;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 synchronise the clocks on these systems.

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 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 Radio 2 Breakfast show, although usually only in jest since the actual event happened rarely. Different BBC Radio stations approach this issue differently. Both BBC Radio 1 and Radio 2 generally take a more laid-back approach with the pips, usually playing them over the closing seconds of a currently playing song or a jingle 'bed' (background music from a jingle), followed by their respective news jingles. 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 Comic Relief's 2005 Red Nose Day, the BBC developed a "pips" ring-tone which can be downloaded.

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 8 am 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 used in both 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.


 * Argentina - all news/talk stations (Radio Nacional, Radio Mitre, Radio Continental, Radio 10, Cadena 3, etc.) air the six pips similar to the BBC every hour, and 3 pips for every half-hour similar to Catalonia.
 * Australia - pips are used on ABC Radio National and ABC Local Radio at the top of every hour, as well as on Fairfax Media talkback stations- 2UE, 3AW, 4BC and 6PR.
 * Canada - the National Research Council Time Signal is broadcast daily on Ici Radio-Canada Première at 12:00 EST/EDT and on CBC Radio One at 13:00 EST/EDT. It is Canada's longest running radio feature and has been broadcast every day since November 5, 1939.
 * China - China National Radio and all local radio stations use a similar 6-pip time signal on the hour. 5 short lower-pitched (0.25 s, 800 Hz) pips are played to count down the final 5 seconds of the old hour, and a longer, higher-pitched (0.5 s, 1600 Hz) pip is played to mark the beginning of the new hour.
 * Finland - on YLE's radio services the pips are broadcast on the hour.
 * France - the station France Inter broadcasts four very short pips every hour, which are almost invariably crashed. The last pip, which is as long as the other ones, marks the top of the hour. Some local stations of the France Bleu network also air four pips that are a little longer than Inter's.
 * Germany - Deutschlandfunk broadcasts four beeps every hour, the last one being longer than the others; between 05:00 and 18:00 on weekdays they are broadcast every half-hour and often omitted at 21:00 when there is no news programme scheduled. Similarly, Deutschlandradio Kultur uses six pips, the last one being longer than the others.
 * 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.
 * Hungary - the national radio channel Kossuth broadcasts five stereophonic pips at the top of every hour, the fifth being longer than the others.
 * Ireland - six pips are broadcast before news bulletins at 07:00, 13:00 and 24:00 on RTÉ Radio 1.
 * Israel - Kol Israel's hourly newscasts begin with six tones, with the sixth tone being longer.
 * Italy - The National Italian Radio "Rai" uses 6 tones to signal exact time in all its stations. They differ in the timing: Rai Radio 1 tells the hour. Rai Radio 2 tells on the half hour. Rai Radio 3 signals the 45 minute of selected hours. All the signals come from the Istituto Metrologico di Torino, the national study centre for measure and time. Also on Rai Radio 1, Rai Radio 2 and Rai Radio 3 tells at 6 o'clock on start the new day.
 * Japan - NHK Television formerly used three short pips played at :57 to :59 of the clock ident and a longer three-second pip from :00 to :03 just before the start of news programmes. The longer three-second pip can however be crashed shortly after the :00 mark on certain special events or if there was time constraints.
 * Malaysia - RTM radio stations use the pips hourly before the news broadcast but only the top-of-the-hour pip is sounded. Until late 2012, the time signal is simply a short pip on the 59th second before the hour and a longer pip on the top of the hour. In a news report in The Star on 1 January 1982, the pips were used to sound similar to the BBC's.
 * Netherlands - only three pips are now used (until 1991 there used to be six).
 * New Zealand - the equivalent of BBC Radio 4, Radio New Zealand National, plays the six pips at the top of every hour.
 * North Korea - the pips are heard on Voice of Korea before its startup at 17:00.
 * Poland - Polish radio have 5 pips and 1 beep before the hour.
 * Sindh The Sindhi language news channel KTN News plays 5 pips at the start of each news hour.
 * Spain - the signal is broadcast by almost all radio stations, even by music stations, but depends on the frequency: music stations usually use pips on the hour, but most of the non-musical stations 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. This station in particular uses only 4 pips, typically the two last using two different frequencies (resulting in a modern rhythm). Other musical radios like Máxima FM and M80 Radio, both owned by PRISA, and Europa FM use a similar effect.
 * Catalonia, Spain - 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.
 * Switzerland - The first channel of the Swiss radio used to play three short pips, the third being higher than the others. It seems to have disappeared now.
 * United States - the pips can be heard on the Middlebury College radio station WRMC.
 * former Yugoslavia- JRT broadcast the six pips before the news (on the hour) on radio as well as on television, before the start of the TV Dnevnik at 8:00 pm. The broadcast on TV was stopped in 1974 because the TV Dnevnik was moved to its current term at the bottom of the hour (7:30 pm).