Home > Greenwich Time Signal
The Greenwich Time Signal or BBC pips is a time code heard on some BBC radio programs at the start of the hour, most notably on Radio 4 and the World Service.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 which, for the five leading pips, lasts a tenth of a second, while the final pip lasts half a second. When a year has a leap second, seven pips are used. The leap second is also the explanation for the sixth 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. On Radio 4, at start of the 6 o'clock evening and midnight news the pips are replaced by the chimes of Big Ben, where the first chime represents the start of the hour. Since 1999, the pips have also been included into David Lowe's branding music and on-the-hour countdown of BBC News 24 and the resulting relaunch of BBC network news.
The pips have been broadcast since 1924, and were the idea of the Astronomer Royal Sir Frank Watson Dyson and head of the BBC John Reith. The pips were originally controlled by two mechanical clocks located in the Royal Greenwich ObservatoryThe original site of the Royal Greenwich Observatory RGO , which was built as a workplace for the Astronomer Royal, was on a hill in Greenwich Park in Greenwich, London, overlooking the River Thames. The Prime Meridian, to which longitude refers, went thr that had electrical contacts attached to the pendulumA gravity pendulum is a weight on the end of a rigid rod, which, when given some initial lift from the vertical position, will swing back and forth under the influence of gravity over its central (lowest) point. A torsion pendulum consists of a body suspes. Two clocks were used in case of a breakdown. These sent a signal each second to the BBC, who converted them to the audible oscillatory signal that is broadcast.
Today the pips are timed relative to UTC, obtained from an atomic clockAn atomic clock is a type of clock that uses an atomic frequency standard as its counter. Early atomic clocks were masers with attached equipment. Today's best atomic frequency standards (or clocks) are based on more advanced physics involving caesium bea located in the basement of Broadcasting HouseBroadcasting House is the headquarters of the BBC in London, England. Situated in Portland Place, it is normally home to Radio 2, 3, 4, 6 Music and BBC 7. Architect G Val Meyer designed the building, which was officially opened on May 14 1932 and is now G that is synchronised with British TelecomBT Group plc (which trades as just BT and is commonly known by its former name, British Telecom is the privatised former British state telecommunications operator. It is still the dominant telecommunications provider in the United Kingdom. History of BT A's Rugby time signalThe MSF time signal is a broadcast from Rugby, Warwickshire based on time standards maintained by the British National Physical Laboratory. The transmitted signal has an ERP of 15 kW, on a frequency of 60 kHz, the same frequency used by WWVB. MSF is a rad and GPS. Although only normally broadcast on the hour, the signal is also generated at quarter-past, half-past and quarter-to every hour.
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 accurate for people living 100 miles from Broadcasting House. The pips are therefore most exact for people living in Leicester, Norwich, Swindon and Calais in France.
Newer digital broadcasting methods have introduced even greater problems for the accuracy of the pips: on platforms which use digital compression such as DAB, digital satellite and Freeview the pips are no longer exactly on the hour. The encoding and decoding of the digital signal causes a delay, usually a few seconds.
