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Celebrating 80 years of the Speaking Clock


First introduced in Britain on the 24 July 1936, the Speaking Clock was created specifically by the General Post Office (GPO) to settle disputes over time. Prior to this the nation was largely run on mechanical wind-up clocks that were prone to drift and increasing numbers of people were ringing telephone exchanges to ask the time.

Operators had been trained to check the exchange clock on the wall and say ‘The time, by the exchange clock, is…’ but this was not precise to the second and operators could not always answer when the caller wanted. So, it was decided that there should be telephone number people could ring to be given the correct, accurate time.

The Post Office had a long history of helping people set their clocks from the days when many towns still operated on local time before the railways arrived, which made it essential for everywhere to be operated on a standardised Greenwich Mean Time. Before that, when it was midday in London it might have been only 11:49 a.m. in Bristol. Apparently when the mail coach would arrive villagers would gather around the coachman to get the political gossip and train drivers would announce what the time was according to their timepieces, which had been set in London. This custom is thought to be where the phrase ‘passing the time of day’ originated.  

The Golden Voice

The first voice of the Speaking Clock was London telephonist Ethel (also known as Jane) Cain who was selected from a pool of 15,000 telephone operators who worked for the GPO in a nationwide competition to find the ‘golden voice’. The judges were poet laureate John Masefield, actress Dame Sybil Thorndike and chief BBC announcer Stuart Hibberd and Ethel was awarded the princely sum of 10 Guineas (the equivalent of £10.50 today) for her work. Both the service and Miss Cain became an instant hit – people wanting to know the time were no longer clogging up the telephone lines calling just to ask the operator the time and Cain’s crisp pronunciation, particularly of the word ‘precisely’ (used at the start of each new minute), proved popular. In its first year of operation the service logged around 13 million calls, that’s over 35,000 a day!

Accurate to one tenth of a second

The accuracy of the clock was calibrated and corrected by referencing to a time signal from the Royal Greenwich Observatory, broadcast by Rugby Radio Station. Time announcements were made by playing short, recorded phrases or words in the correct sequence, giving the Greenwich time correct to one-tenth of a second. The original mechanism consisted of an array of motors, glass discs, photocells and valves, taking up the floorspace of a small room and the message was recorded optically onto the glass discs and replayed, rather like a film soundtrack. Two speaking clock machines were made, in case of breakdown. In comparison, the current digital Speaking Clock (first introduced in 1984), with built-in crystal oscillator and microprocessor logic control has no moving parts at all, occupies no more space than a small suitcase and is assured to be accurate to five thousandths of a second. The current source of UK time is provided, but not monitored, by the atomic clock signals provided by the National Physical Laboratory. Yet, the initial equipment, for those days, represented state of the art cutting edge technology; an automated system that was ahead of its time.


Initially, the service was only available in the London directory area from the Holborn Exchange, but was rolled out nationwide in 1942. If you lived in one of the major UK cities – London, Birmingham, Edinburgh, Glasgow, Liverpool or Manchester – you would obtain the service by dialling the letters TIM, which corresponded to the digits 846 on a dial phone, whereas other areas dialled 952. Engineers had conceived TIM as a shorthand for time, but it wasn’t long before the service colloquially became known as ‘Tim’.

1963 – All change!

The first Speaking Clock was taken out of service in 1963, replaced by a more modern transistor version, using a magnetic drum, and complete with a new voice. Pat Simmons, a London telephone exchange supervisor won the second competition to find a voice for the Speaking Clock and a £500 prize.

Significant others

In 1984, Brian Cobby became the first male voice to take over the clock. An assistant supervisor at Withdean exchange in Brighton, Brian had been an actor by profession before joining British Telecom and recorded the ‘5-4-3-2-1…Thunderbirds are go!’ for the theme tune to the Gerry Anderson TV series.

Surprisingly, there have been only four permanent Speaking Clock voices, although temporary voices have been used on special occasions. The current voice is that of part-time voiceover artist Sara Mendes de Costa, who won the role after entering a competition launched by BT and Children in Need in 2006. Chosen from over 18,000 entrants, Sara took over the helm on 2 April 2007 during Terry Wogan’s BBC Radio 2 breakfast show.

Temporary voices have included Lenny Henry, Sir Ian McKellen, Clare Balding, Fearne Cotton and Chris Moyles for Comic Relief; David Walliams, Jo Brand, Davina McCall and Gary Barlow for Sport Relief; Mae Whitman as part of a deal to promote the Disney production of Tinkerbell and Alice Roland, a 12-year-old schoolgirl who won a BBC Newsround competition to represent children’s charity ChildLine.

The message

Every ten seconds a voice announces: ‘At the third stroke, the time from BT will be [hour], [minute] and [second] seconds’ followed by three pips. ‘Precisely’ is substituted for the seconds portion of the announcement for times which are an exact minute. Likewise, announcements for times between the hour and one minute past the hour substitute ‘o’clock’ for the minutes. Each day the speaking clock makes 8,640 announcements.

On the occasion of a leap second – such as at 23:59:60 on December 31 2005 – an extra second pause is added between the second and third beeps to keep the clock in sync with Coordinated Universal Time.

When the service was first launched, calls to the Speaking Clock cost one penny from home and ‘tuppence’ from a phone box. After listening for 90 seconds, the caller, if they had not hung up already, would be automatically disconnected. Today a call to Timeline cost 38.9p per minute.

The Cold War

During the Cold War the speaking clock network was designed to be used in case of a nuclear attack. Had such an attack taken place then the clock would have broadcast messages from Strike Command at RAF High Wycombe to regional police stations. In turn, this would have triggered automatic warning sirens and alerts sent to Royal Observer Corps monitoring posts.

Using an existing, rather than dedicated, system mean that it was effectively under test all the time – customers would report any faults as soon as they occurred rather than risk having a problem with a dedicated line which would not be noticed until it was needed.

Modern developments

The undisputed accuracy of the Speaking Clock led Accurist Watches to sponsor the franchise in 1986, although this came to an end in 2008.

With the introduction of Subscriber Trunk Dialling, allowing long-distance calls to be dialled directly without operator assistance between the 1960s and 1980s, the Speaking Clock dial code changed to 80 and later 8081. By the 1990s it was standardised to 123 if dialling from a BT Phone line and the number still in use today. BT also renamed the service ‘Timeline’ around the same time.

Big Ben, the bell belonging to the world’s most famous clock, checks its time with the Speaking Clock and many major organisations have permanent feeds from the clock to their internal phone systems so that employees can check the time without making an external call. All ITV television programmes are also synchronised to the Speaking Clock – for example, when the local station goes over to ITN or BBC for the news, this is done ‘at the third stroke’.

Do people still use the clock today?

Yes! At its height the speaking clock commanded around 250 million calls per year. Despite all the digital devices where time can accessed instantly, the Speaking Clock service still receives in the region of 12 million calls a year, with demand peaking on four time-sensitive days: New Year’s Eve, the two days a year the clocks change and Remembrance Day.

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