So what you hear is "At the Third Stroke it will be one, twenty-one and forty seconds".
In 1963, the original device was replaced by more modern recording technology using a magnetic drum
This system gave way to the present digital system in 1984, which uses a built-in crystal oscillator and microprocessor logic control
The complete apparatus comprises solid-state microchips, occupies no more shelf space than a small suitcase and has no moving parts at all
The BT service is assured to be accurate to five thousandths of a second.
In 1986, BT allowed Accurist to sponsor its franchise, the first time a sponsor had been used for the service
In the latter years of this sponsorship, it cost 30 pence to call the speaking clock. Accurist announced its withdrawal from the deal and the launch of an online "British Real Time" website on 24 August 2008.
During the Cold War, the British Telecom speaking clock network was designed to be used in case of nuclear attack to broadcast messages from Strike Command at RAF High Wycombe to HANDEL units at regional police stations. From there, automatic warning sirens could be started and alerts sent to civil defence volunteers equipped with manual warning devices
The rationale for using an existing rather than a dedicated system was that it was effectively under test at all times, rather than being activated (and possibly found to be faulty) only in the event of war
The signals to automatic sirens were sent down the wires of individual (unaware) subscribers for the same reason — a customer would report any fault as soon as it occurred, whereas a problem with a dedicated line would not be noticed until it was needed.
A version of the speaking clock was also used on recordings of the Houses of Parliament made by the BBC Parliament Unit, partly as a time reference and partly to prevent editing
On a stereo recording, one track was used for the sound and the other for an endless recording of the speaking clock — without the pips, as these were found to cause interference.
On the occasion of a leap second, such as at 23:59:60 on December 31, 2005, there is a one second pause before the beeps, thus keeping the speaking clock in sync with Coordinated Universal Time
The current source of UK time is provided, though not monitored by the National Physical Laboratory, UK. Since 2003, the British speaking clock has changed voices four times
All changes have occurred on days when the clocks have switched from standard time to daylight saving time or vice versa
This is due to the fact that 123 is most commonly dialled on these days.
The speaking clock service is not available on the Orange or 3 Mobile mobile telephone networks, as they use 123 as the number for their Answerphone services.
The BT Speaking Clock receives around 60 million calls a year.
List of voices heard on the British "BT Speaking Clock"
Ethel Jane Cain, first permanent voice: from July 24, 1936 to 1963.