What's 74 years old and makes BT a staggering £21 million pounds a year? Amazingly, when most people have an easy, free way tot ell the time - their mobile phone - it's the Speaking Clock.

Since 1936, the Speaking Clock has been ticking along 24 hours a day, seven days a week, 365 days a year. Also known as TIM, from the first three letters of TIME dialled on the old alpha-numerical dial phones, it remains a stalwart of British time keeping.

Originally only available in the London area until a nationwide expansion in 1942, TIM has had three different official voices and three changes of technology and still commands a lot of attention today.

Holborn exchange london

LONDON CALLING: Holborn Exchange, London - Speaking Clock [Image credit: BT Heritage]

Even before TIM was rolled out nationally it clocked nearly 13 million calls in its first year alone. Today, the Speaking Clock receives almost two million calls a week with a grand average of over 70 million calls a year, at a cost of 30p per call. So it's hardly surprising that it hasn't been retired.

"It's hard to say why the Speaking Clock is popular," a BT spokesperson told TechRadar. "The Speaking Clock has been around for 74 years so a lot of people have grown up with dialling 123. BT's Speaking Clock is a national institution, viewed with great affection by the general public."

We'll assume the callers aren't all like an office worker interviewed for a newspaper article in Bristol who confessed she phoned the clock several times an hour – "but not to find out the time, just to look as though I'm working."

The voice of the Speaking Clock

Back when it all began it was a lady by the name of Ethel Cain (also known as Jane Cain) who was the first voice of the talking clock from 24 July 1936. She won a grand prize of £10.50 in the competition to discover her voice and remained a familiar presence until 1963.

"The actual recording wasn't as strenuous as most people seem to think," said Jane Cain, "The real work was done by the engineers of the Post Office. The way I recorded it was in jerks as it were, I said 'At the Third Stroke' and then I counted from One, Two, Three Four, for the hours..."

Jane cain

ON THE THIRD STROKE... Jane Cain, first voice of the speaking clock in 1936, with the glass discs that carried the recordings she made [Image credit: BT Heritage]

In 1963 Miss Pat Simmons, a supervisor in a London telephone exchange, was the lucky winner of the next competition to find a new voice for the Speaking Clock. Legend has it that the original MK1 Speaking Clock, donated by BT to the British Horological Institute in Newark, stopped working on the day that Pat Simmons died in October 2005.

From the 1930s until the 1980s she continued the tradition of a female voice for the Speaking Clock until Brian Cobby was picked from over 5,000 applicants in the BT's Golden Voice competition to take Miss Simmons' place on 5 December 1984.

Brian cobby and patricia simmons

DOUBLE ACT: Brian Cobby and Patricia Simmons - the third and second voices of the speaking clock respectively [Image credit: BT Heritage]

In an interview with David Bramwell Brian Cobby said, "One young female reporter stuck a mic under my nose and said 'do you think women might be alarmed hearing not a woman's voice, but a man's?' I replied, 'I'd hate to alarm any woman, but I'm sure that by the third stroke they'd have got to like me!'"

New voices

Brian Cobby ran the lines for almost 22 years with two brief interruptions – Lenny Henry's gig to raise money for Comic Relief and 12-year-old Alicia Rowland's week long stint after winning a competition in aid of ChildLine.

Alicia was the first, and only, children's voice to appear on TIM and she ran for a week from 13 October 2003. Lenny Henry commandeered the clock for two weeks to raise money for Comic Relief and used a different character every day for the entire time. His run was so successful, raising £200,000 for the charity, that he redid it in March 2009.

In 2006, 70 years after TIM's inception, BT ran another competition to find a replacement voice for Brian Cobby and to raise money for Children in Need. Over 18,500 people entered, raising a hefty £200,000 (again) for BBC Children in Need. The winner was Sara Mendes da Costa whose warm and friendly voice has graced the 123 lines ever since.

Brian cobby

DIGITAL SWITCHOVER: Brian Cobby: the first male voice of the speaking clock with digital equipment [Image credit: BT Heritage]

"The Speaking Clock only has 79 different announcements which are then copied as many times as are needed for the 24-hour period, and spliced together by the technical engineers," Sara told TechRadar.

"If I had recorded everything just the once it would have taken about 45 minutes. The first time I was so excited that I over projected. I listened back and went 'Eeooo! Much too in your face', so I did it again more calmly."

There were some interesting additions to the Speaking Clock since da Costa took over, not least of which was Lenny Henry reprising his Comic Relief role in March last year. Tinkerbell, voiced by Mae Whitman, squeaked along in time for three months in 2008 in a somewhat controversial deal with Disney. Even the pips were replaced with the Tinkerbell tinkle.

Increasing accuracy

Today the talking clock is accurate to within five thousands of a second, a far cry from the original accuracy of one-tenth of a second. Not only that, but Big Ben, TV programmes like the News at 10, and many large organisations all set their systems to run in conjunction with TIM – all reading their time from the "third stroke".

Back when TIM first started out the clocks were electro-mechanical devices with the different parts of the time announcement recorded on rotating glass discs and broadcast at intervals of 10 seconds. In 1963 these were replaced by a revolving magnetic drum and, in 1984, the Chronocal system, digital time, was introduced with an accuracy of up to five milliseconds.

Still, what better way to conclude than to quote a part of the original Post Office briefing from the 1930s which states, "In view of the possibility of certain members of the public becoming so enamoured of the golden voice that they are impelled to listen to it for an indefinite period, an automatic device disconnects the circuit at the end of ninety seconds."

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Liked this? Then check out 5 technologies to thank the 1950s for

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