Greenwich Time Signal 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. 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 kHz tone (about halfway between
BBC Radio 4 7pm its DAB output is usually in mono, even though many of its programmes are made in stereo (including its flagship drama "The Archers"), these can be heard in stereo only on FM, Digital TV on Freeview & Freesat (Ch. 704), Sky, Virgin and on line via BBC iPlayer radio. BBC World Service, which uses BBC Radio 4 FM & DAB frequencies between 01:00am and 05:20am, is in stereo, but only on Radio 4 FM & DAB and not on its own dedicated DAB channel. BBC Radio 4 Extra broadcasts in mono on DAB, but has always been in stereo