At the third stroke it will be one... thirty-two... and twenty seconds.
- Douglas Adams, So Long, and Thanks for all the Fish

The first automatic time service was available to San Franciscans at the end of the 19th Century. Callers could listen to an observatory clock for a minute, and then decode the clicks and buzzes heard against detailed instructions. This intricate and complicated system could then be used to set a pocket watch. However, the first speaking clock was introduced in the USA in 1927. It then arrived in Paris in 1933, The Hague in 1934 and Switzerland in 1935. It came to London in 1936.

Before the invention of the speaking clock, if a person wanted to know the time and didn't have a watch or clock to hand, they had to ring the operator. The operator would refer to the exchange clock (the most accurate clock available), and then inform the caller: 'The time by the exchange clock is...'. The time was not precise, nor was it an immediate response. The speaking clock came into being in the UK on the 24 July, 1936. It was the first of the phone pre-recorded information services, and was initially only available in the London directory area. To access the service, subscribers would dial the first three letters of the word 'time'. At that point telephones had letters associated with each of the numbers, much like mobile phones today, thus the number actually dialled was 843. Dialling T, I, M lead to its common name 'TIM', though officially its name is 'Timeline'. TIM went national six years later.

In the first year of its introduction, TIM received almost 13 million calls. Today, more than 135 million calls are made to the service every year. It is important in the smooth-running of a number of organisations. The timing of ITV TV programmes is synchronised to the clock, and even a Hong Kong factory relies on TIM for the in-built clock of its VCR handsets.

You can, of course, hear the dulcet tones of TIM by calling 123 in the UK. Calls cost 10p per minute.

Clock Devices

The initial clocks for TIM were electro-mechanical devices, designed and constructed at the Post Office Engineering Research Station at Dollis Hill, London. The different parts of the time announcement were recorded on rotating glass discs, and were broadcast at intervals of ten seconds using technology similar to that employed to play the soundtrack of a film. A pair of clocks was housed in the Holborn Tandem Exchange. In 1942, a second pair of clocks was housed in Liverpool as a precaution to prevent failure of the service. A double 'ring-main' circuit was used to feed the centres to exchanges throughout the UK. Roughly speaking, one clock from each centre was used to tell the time to half the country. Needless to say, it used cutting-edge technology and this system was used until 1963, when the new system was introduced.

The third version of the clock was made by Roberts and Armstrong of Wembley to a design invented by a Post Office Research Station. Roberts and Armstrong took over the commercial development of the design and exported a number of units. Two clocks were held in Kelvin House, L/TCN (London Trunk Control North). Each had its own control and alarm equipment, with shared equipment used to monitor outputs and check accuracy. A car radio was fitted near to the bottom. This was used to provide emergency standard time signals in the event of the normal correction signals failing to arrive from Rugby.

Playing the Recordings

There were two announcement machines. Each contained a magnetic drum with 79 tracks (recordings), which rotated at a rate of 30 revolutions a minute. 12 replay heads were used and, the phrase 'At the third stroke' and the six-second announcements were reproduced from fixed heads. The announcement of the hours was obtained from one head, stepped every hour along the 12-hour tracks. Four heads were used for the minutes, each of which covered 15 tracks. The heads were moved through via the use of 'Geneva-type' gear boxes.

Tones of 5.5, 6.5 or 7.5kHz were recorded onto each track, which were used to detect if the announcements of the clocks were out of step. These pilot tones were then removed from the audio output by a low pass filter. The 'pips' were produced by a tone of 1000Hz for a duration of 100ms. This was controlled by a shutter, which interrupted a beam of light landing on photocells.

This system was used until 1984, when it was replaced by the current digital system.

Today, the clock has an inbuilt crystal oscillator and microprocessor logic control, solid-state microchips and it takes up the space of one small suitcase. There are no moving parts whatsoever. Quite a change from its original parent, which took up the space of a small room! Again, it is compared to the NPL atomic clock in Rugby twice a day. It is expected to be accurate to within one tenth of a second. The switch from the magnetic drums to the current system was made by Colin Baker, who in 1984 played the Timelord Doctor Who.

The Golden Voices

Not surprisingly, the voice of TIM has changed throughout the years. At the time of writing, only four people have had their voice recorded for the speaking clock. Traditionally, selection of the voice has been by a national competition among the telephone staff, with the clearest, and most untheatrical voice being chosen.

Miss Jane Cane

Jane Cane, a London telephone operator was the original voice of the clock. She was the 'golden voice' from 1936 until 1963.

Miss Pat Simmons

Pat Simmons was a supervisor in a London exchange. She made her recording in 1963, and handed the gauntlet on in April 1985.

On an episode of Antiques Roadshow in October, 2008, a gentleman from the National Maritime Museum explained how the machine on display at the museum suffered motor failure on the day Pat Simmons died.

Mr Brian Cobby

Brian Cobby, an assistant supervisor, was chosen to be the first male voice of TIM on the 5 December, 1984. His tones were first heard at 11 o'clock on 2 April. He did cause a bit of a stir, because of the female precedent.

By profession, Brian is an actor, and is also very well known for a voice-over he created in 1965 - the countdown for Gerry Anderson's TV puppet series Thunderbirds.

Mr Lenworth George Henry

For the short period of time from 10 March to 23 March, 2003, callers to the speaking clock were treated to the voice of comedian Lenny Henry. This was done in aid of Comic Relief Red Nose Day, and is expected to raise £200,000. Every day, a different character voice could be heard. They also altered the noise of the pips!

Miss Alicia Roland

Following a competition on BBC Television's Newsround, Miss Roland was the temporary voice of the clock between 13 October and 20 October, 2003. This was for the children's charity, Childline and so, before the time was announced, Miss Roland stated 'It's time to listen to young people.'

Ms Sara Mendes da Costa

This telemarketer and voiceover artist became the new voice of the speaking clock from 2 April, 2007. She was recruited following a competition to find a new voice, held to mark the BT clock's 70th birthday and in order to raise funds for the BBC's Children in Need.

Accurist

As a result of the accuracy associated with Tim, Accurist Watches became interested in sponsoring the service. The recording was changed at the end of March 1986 to reflect the fact that it was sponsored by Accurist Watches Ltd. The clock now says 'At the third stroke, the time sponsored by Accurist, will be...'.