Words & illustrations by Andrew Emmerson
This is an 'entry level' guide to the subject, with links
to resources on other websites.
Clicks and buzzes
people do before the speaking clock was invented if they
wanted a time check? Simple: they rang the operator and asked
her the time by the exchange clock on the wall, but this was
not precise to the second, nor could the exchange always
answer just when the customer wanted. The first genuine
speaking clock machine was introduced in the USA in 1927,
coming to Paris in 1933, The Hague in 1934 and Switzerland in
1935. But automatic time service (of a Heath-Robinson kind)
had been available to telephone users in San Francisco since
the late 19th century; by listening for to an observatory
clock at least a minute and decoding clicks and single and
double buzzes against some detailed instructions you could
set a pocket watch - but it helped if you already knew
more or less what the time was. A proper speaking clock is
far more convenient...
The first British clock
Speaking Clock service was inaugurated in London on 24th July 1936 with a pair of clocks in
Museum Telephone Exchange, Holborn (they had been developed by the Post Office
Research Station at Dollis Hill, North London). Distribution of the
service is by means of relay sets installed in the Tandem Exchange which
allows up to 100 simultaneous calls to be connected to the clock.
A second pair
of clocks was installed at Lancaster House in Liverpool during 1942 as a
safeguard against interruption, with a 'ring main' connecting
both sets of clocks by diverse routes to all exchange centres
in the country.
Speaking Clock showing glass discs
Picture dated 1936
Speaking Clock under test
Picture dated 1936
- the first
speaking clock mechanism, which used photographic storage in revolving glass
Holborn Exchange, London
Picture dated 1950
- a technician
adjusts the amplifiers of the first speaking
clock mechanism; note Telephone No. 121 and Bellset
No. 20 on the wall at rear.
Picture dated 1936
P1281 - technician checking the speaking
clock apparatus at Holborn Exchange
Picture dated 1936
Click here for more pictures of
the Speaking Clock Mark I
Click here for an
assembly drawing of the Speaking Clock Mk I
is a 'popular' description of TIM, taken from Practical
Mechanics magazine, May 1938 (page 425)
A brief description of TIM the
G.P.O. Clock, which has answered
over 20,000,000 calls since its installation just over
a year ago.
By William G.
Clocks are not new inventions, for clocks of this nature
have been in use for a considerable time in Europe, Asia
and elsewhere. There is nothing, however, quite like TIM,
the wonder instrument of the Post Office. The sounds
which come from this clock are recorded on glass discs,
reproduction is remarkably clear and the discs are
practically everlasting. Eighteen months' severe testing in the Post
Office research station has resulted in the clock giving
an extremely accurate performance. It is only possible,
at present, to hear this clock in the London district,
but it is hoped to extend the service to other
large towns in the near future. Proof of the popularity
of this clock is shown by the fact that over 20,000,000
calls have been made since its installation a little more
than a year ago. The public's appreciation of accurate
time is evident, for 37,000 people asked the time between
8 a.m. and zero hour on the last Armistice Day.
The main part of this ingenious
clock consists of four circular glass discs like
gramophone records. On each disc are photographed the
various numbers and phrases as spoken into a special microphone
by Miss J. Cain, who is now known as "the girl with
the golden voice." The sound tracks, similar to
those on the edge of a talkie, film, are arranged in a
series of concentric circles.
Upon dialling the letters TIM (code 846) a subscriber is connected with the clock and hears a voice
repeating the time. The announcement is phrased as
follows: "At the third stroke it will be ten,
twenty-five and thirty seconds precisely" (or
whatever time it is) followed by pip ... pip ... pip. The
period of listening lasts from 1.5 minutes to 3 minutes,
after which the call is automatically cut off.
Of the four discs, two share the
minutes, each having thirty sound tracks. The other two
discs are used for the hours and seconds. The hour disc
has twelve tracks and the seconds disc six tracks. The
various words of the sentences are also recorded on the
various discs, so that when an announcement is made all
the discs come into use.
The reproduction if speech from the
sound tracks is produced by focussing a ray of light on
the discs and letting the light fall onto a
photo-electric cell mounted on the opposite side. The
electric current from the photo-cells is amplified, the volume of sound being such that two hundred people may
listen at the same time.
The light rays are obtained from
small electric lamps and a number of lenses. Each disc
has its own lamp and set of lenses, usually referred to
as the "scanners." The "scanners" are
mounted on carriers which move in and out of the discs in
order that the ray falls on the appropriate track.
Movement of the "scanners" is governed by cams
mounted on the carrier shaft. The cams work in
conjunction with three ratchet wheels, one each for the
hours, the minutes and the seconds, the ratchet mechanism
being operated by trip magnets.
A very accurately controlled
electric motor drives both the discs and the scanners.
Extreme accuracy is ensured, for the motor speed is
governed by a master clock having a free pendulum,
beating seconds. Attached to the bottom of the pendulum
is a slide having a number of transparent areas. Placed
in front of the slide is an electric lamp, a series of
lenses and a narrow vertical slit, and behind the slide
is a photocell.
The current produced by the light
falling on the photo-cell is amplified and used to give
impulse to the pendulum. As long as the pendulum
vibration. is constant, no impulse is given, but as soon
as the vibration decreases, current from the photo-cell
is used to increase the vibration to normal. In order
that the error between the third pip and true time shall
not be more than 0.1 second, the master clock is
connected by relays to Greenwich Observatory and
synchronisation takes place every hour. Should the clock
be out of step with Greenwich time, one of a number of
relays is operated, causing the current in the coil of a magnet - which is placed beneath an armature fixed to
the pendulum rod - to vary. By varying the force the
rate of the pendulum can be advanced or retarded and
brought into step
Actually there are two clocks
installed at the exchange. Erected side by side, both are
running continuously. Should the first clock break down
or have an error in excess of a tenth of a second from G.M.T. at any hour, the second clock automatically
comes into action. The Post Office have spared no energy
to make this service the most accurate possible and they
have been rewarded. TIM has already netted the sum of
Full technical details of the Speaking Clock were given in
a number of Journals. Many of these can be viewed in the Downloads
section at the bottom of this page.
P4728 - the room
where the first speaking clock was installed
Close up of the Speaking Clock Mk 1
Inauguration of the Speaking Clock at Holborn
Picture dated 1935
World War II technology from the Speaking Clock was applied
to other interesting projects. Special noise-cancelling
microphones and headphones were devised by the Post Office
for tank use. Deep below their Dollis Hill research station a
special chamber with deafening sound effects was constructed
to simulate a tank's interior. Producing the sound
effects with which to test these devices was another matter;
recordings on 78rpm gramophone records would not last long
enough and the chosen solution made good use of other Post
First of all recordings were made - on
direct-cut disk - of a tank rumbling past a microphone. Ten-second recordings made in this way were transferred to
35mm film by the Crown Film Unit (a new name for the
old Post Office Film Unit) and a two-second long section
finally transferred to glass disc, for playing continuously
on a speaking clock machine.
Apparently the joint in the
recording and the two-second repetition were not noticeable
in use. Similar machines were made for the Royal Air Force;
these generated continuous background aircraft noise effects
for training radio operators. Four different aircraft types
were covered, at normal speed and at absolute maximum. Yet
another machine was for training fighter pilots; this was a
twin-channel simulator, providing continuous aircraft noise
and spasmodic machine-gun effects as and when required.
During the Cold War the speaking clock network was designed to be
used in case of nuclear attack to broadcast messages from Strike Command at
High Wycombe to regional police stations.
From there, automatic warning sirens could be started and alerts sent to
Royal Observer Corps monitoring posts. The design used the existing
Speaking Clock circuit that ran around the UK rather than a dedicated
system. This ensured that any break down in service would be noticed
The signals to sirens were sent down the wires of individual subscribers
for the same reason. As customers would report any fault as soon as it
occurred this ensured that the line would be repaired as soon as possible.
A Mark 2 clock, which was a
replica of the Mark 1, using similar photographic soundtracks but
with quartz crystal oscillators for greater accuracy was produced in
The accuracy of the new clocks was plus or minus 5ms when
corrected hourly, whereas the Mark 1 clocks were plus or minus 100ms when
corrected hourly. The correction is automated in the mark 2.Due to the new design
with it's much improved accuracy, the
Australian Postmaster General ordered clocks for Melbourne and Sydney.
These Mark 2 clocks can now be viewed in the National Communications Museum
Mark II Rack Layout - EX89000
Mark II Schematic - EX28925
Mark II Room Layouts - EX28851
Mark II Assembly - EX43400
Mark 2 - Operated from 1954 to
1990 in the City West Exchange, Melbourne
Mark 2 clock installation
Posters advertising the Australian
Speaking Clock service (1954)
The Post Office decided in the early 1960's that due to
the London clocks requiring relocation and the deterioration of the clock
wiring it would be best to renew the clocks and install them in their new
In 1963, the Mark 2 clocks were
superseded by the Speaking
Clock Mark 3, which used modern recording technology of a magnetic media.
This was a rotating metallic drum with a thick layer of magnetically loaded Neoprene and driven from a crystal controlled oscillator.
The crystals are maintained at a temperature of 50 degrees C in an oven.
The new London clocks were also installed in the Trunk North Control which had
un-interrupted power and a much better working environment. They came
into service in October 1963 and the Liverpool clocks followed in October
1963. In the interim period from May to October the prototype clock at
the GPO Research Station at Dollis Hill acted as a standby to cover the London clocks
which were serving the entire country.
Synchronisation also changed from Greenwich to Rugby. This was now
daily and the feed was by landline.
These Mark 3 clocks, using a revolving magnetic drum, replaced the original
speaking clock introduced in 1936. The 79 separate phrases
required for a 12-hour clock were recorded as circular tracks
spaced 1/16 inch apart along the length
of the drum. The pips were not recorded on the drum but were
derived from an oscillator. The Speaking Clock
had accuracy to approximately 1/20
second. Like the first clock, the second speaking clock had
its accuracy calibrated and corrected by referencing to a
time signal from the Royal Greenwich Observatory, broadcast
clocks were installed, one in London and one in Liverpool and were joined
together by the dedicated double ring-main trunk circuit that ran around
England. Under normal conditions one clock at each centre supplies
approximately half the country, but under fault conditions either
installation could take the full load.
The company that manufactured the rotating magnetic drum
part of the Speaking Clock was Roberts & Armstrong (Engineers) Ltd of North
Wembley. They took on the licence from the British Post Office to
manufacture complete clocks for the telecommunications authorities of
Denmark, Sweden and the Republic of Ireland, and a third (spare) clock for
the British Post Office. The latter was installed in Bow Street, London. The
European clocks were modified for the 24-hour system by lengthening the drum
and adding extra heads. Roberts & Armstrong subcontracted the electronic
aspects to the Synchronome Company of Westbury. The clocks were designed to
run non-stop for 20 years.
Speaking Clock Mark 3
Speaking Clock Mark 3 - close up
Speaking Clock Mark 3 -
control covers open
Picture taken in 1967 at Judd Street, London with Pat Simmons
the 1980's British Telecom devised the Mark 4 which was a solid state speaking
clock known as Chronocal. It occupied a 19-inch rack cabinet
about 3U (5.25") tall and based on the ACRE CP85 processor board.
It also included a radio receiver so that it could make use of the 60hz time
correction signal, but still retained the Rugby landline for extra security.
It went live in mid 1984 and could be equipped with either
the Pat Simmons or Brian Cobby voices. This system is solid state and has no moving parts at all.
During the 1980's (possibly 1990's) BT renamed the
Speaking Clock 'Timeline' but the name did not find
Since 2001, Time & Frequency Solutions have supplied the
technology behind the Speaking Clock. Teligent, the telecoms
specialist, supplies the vital switching gear enabling multiple users to
access the system at the same time. The time source used is a Time &
Frequency Solutions M211 Master Clock Timing System with a redundancy
element to ensure continued working even if a fault developed.
20,000,000 calls to TIM in the first year - 1936.
265,000,000 calls to TIM from London users from 1936 -
400,000,000 calls to TIM nationwide from 1936 - 1949.
70 million calls to TIM nationwide in 2006.
30 million calls to TIM nationwide in 2011.
The people behind the voices
Final of Golden Voice Competition for the Speaking Clock
Postmaster General with judges who included Major Tryon and Mr John
Masefield, the Poet Laureate
(Picture dated 21 June 1935)
Finalists of the Golden Voice competition (1935)
The voices of TIM
first voice of the Speaking Clock voice. She was chosen after
a nationwide competition among 15,000 women telephonists and
was awarded ten guineas (£10.50). Until then she used her first name
Ethel but dropped this in favour of her middle name, Jane,
and made a record for the GPO helping other staff improve
their speaking voice. She went on to become announcer for Henry Hall
during one of his broadcast concerts and was offered a film
part by Columbia Pictures under the name of Jane Cain. Born
1st May 1909 - died aged 87 on 19th September 1996.
Ethel Cain recording the speaking clock in 1935
Ethel Cain dialling TIM at Dollis Hill to hear
her own voice tell the time, 20th March 1936
Radio and Television Exhibition, Earls Court, London
Picture taken 1960
Gordon Gow & Richard Peach
In 1953 Gordon Gow, a radio broadcaster and theatre critic, was the
recording voice for the Mark 2 clocks that were exported to Australia.
Gordon was born in Australia and moved to London in the early 1950's.
He was commonly referred to as ‘George the talking clock’.
The original disks were replaced in 1958 with some
recordings, not used in 1953, replacing phrases that were not to the
satisfaction of the Australian Post Office.
Telstra, in 1990, replaced Gordon Gow's voice with that
of Richard Peach, the ABC Broadcaster.
Gordon Gow (Picture dated 1953)
competition was held in 1963 to find a replacement for Miss Jane
Cain's voice for the Mark 3 Speaking Clock. It was won by
Miss Pat Simmons, an Assistant Supervisor in Avenue Telephone
Exchange, London. She was to be heard until Brian Cobby replaced her in 1985.
Pat Simmons recording
Pat Simmons recording
Brian was the voice of the Speaking Clock
from 1985 until 2007.
voice of the Speaking Clock today, he was interviewed and this is an extract
you become the voice of the speaking clock?
I moved to Brighton more
than 30 years ago and got a job with the Post Office,
where I worked for 16 years. In 1984, British Telecom [as
the Post Office's telephone arm became in 1981] decided
to change the speaking clock. They ran a competition
among the staff to find a replacement voice, which had to
be clear and warm with no regional accent. After a series
of regional heats, I beat a lady from Lowestoft in the
final. She became the voice that says, "the number
you have called has not been recognised." I became
the voice of the speaking clock on 2 April 1985 at 11am,
precisely. The telephone lines were jammed with people
trying to listen.
did the announcements take to record?
Just an hour, but it was
hard work. I recorded the times in a studio in London,
where I had to read from a 33-page script. It was
calculated mathematically [only 86 words are actually
used], so I didn't have to go all the way round the
clock. Later, we found that we hadn't taped the 'o'
clock' so I had to drive back up to London just to record
have heard your voice anywhere else?
Maybe. Before I worked for BT I was an actor.
As well as films and some Shakespeare, I did a lot of voiceover work,
mostly for commercials. In 1965, I did one of my most famous voiceovers:
the countdown for the TV programme Thunderbirds.
poster above them looks intriguing...
Yes, it's from a 1959 film
I did, called The Nudist Story. It was billed as
being shown in 'blushing technicolor'. Many years later,
a Sunday paper ran a story, 'Speaking clock in nude
movie'. The picture they printed of me was actually that
of a boy who played my brother, who, alas, was a lot
skinnier than me. I had a great body in those days...
The wording of Brian Cobby's
announcement was altered in 1986 to include the phrase
"sponsored by Accurist " to become "At the
third stroke the time sponsored by Accurist will be...."
Henry is to provide the voice of the speaking clock for the
next fortnight. The comic's Black Country burr will replace
the usual plummy tones of BT's service as part of a Comic
Relief fundraising drive. Callers dialling 123 pay will 10p
for the service, and proceeds from today to March 23 are
expected to raise £200,000 for the charity. Lenny, who is
temporarily replacing Brian Cobby as the voice of the clock,
is only the fourth ever person to take on the role in its
67-year history. He will be putting on a different voice each
day in the hope of encouraging people to ring back. He said:
"I can hardly believe it. Wait until you hear what we've
done to the pips." March 10, 2003
A 12-year-old girl says she is
proud to have become the only child and the first Scot to
record the Speaking Clock in its 67-year history. The
schoolgirl's voice will be heard by up to two million callers
over the next week. Alicia, from Brookfield, Renfrewshire,
beat thousands of children from all over the UK in a
competition to become the voice for a week. The idea is part
of the Big Listen, a week of activities which encourages
adults to listen to young people and raise money for the
charity ChildLine. Organisers estimate Alicia will raise
£200,000 during her week in the job - calls cost 10p and BT
is donating every penny to the good cause. She said:
"It's very nice to be the first child to do this job, I
think it's good for people to hear a child's voice when they
ring up. My friends at school were a wee bit envious
but they've been really supportive, they said they're going
to ring up the clock loads this week." It is only the
fifth time that the Speaking Clock - which began in 1936 and
receives 80 million calls a year - has been changed. 13th October 2003
Sara Mendes da Costa
Born in 1966, Sara Mendes da Costa from Brighton became the fourth
permanent voice of the UK Speaking Clock in 2007.
On 23th October 2006, to mark the BT clock reaching its 70th year, a
competition was launched to find the new modern voice of the Speaking Clock.
Applicants were invited to leave telephone recordings of their voice, with
the proceeds of each call going to Children in Need. Sara Mendes da
Costa, a telemarketer and part-time voiceover artist, was announced as the
winner on BBC One's Children in Need telethon on 17th November 2006.
She was the unanimous choice of a voting panel that included the clock's
previous voice, Brian Cobby, the BBC presenters Natasha Kaplinsky & Alan Dedicoat, and Sir Christopher Bland, chairman of BT Group.
Sport Relief 2012
For five weeks only, David Walliams joined Chris Moyles,
Kimberley Walsh, Gary Barlow and Fearne Cotton as the voice of the BT
Speaking Clock. This was between Wednesday 7th March 2012 and Monday 9th April
To celebrate the new voice, BT ran a competition on
its Facebook page giving fans a chance to win a limited edition David Walliams wall clock. To enter you had to guess the mystery celebrity
voice telling the time that day. If you named correctly your name will
automatically be placed in a daily prize draw to win the prize.
the 9th November 2016, Alan Steadman from Scotland became the fifth voice.
He was a retired Civil Servant and presented a weekly local radio jazz
programme for 33 years.
The original dialling code was
TIM (code 846), short for Time, which was used in London and other major
cities. At smaller locations the code was 8081 or 9-8081.
After the change to all-figure numbering at the end of the
1960s the TIM code was changed to 123 and elsewhere 8081 was
changed to 123 also, some time in the 1990's.
accuracy of the speaking clock is beyond reproach, within
five thousandths of a second in fact. With a built-in crystal
oscillator and microprocessor logic control, the complete
apparatus is made of solid-state microchips and
occupies no more shelf space than a small suitcase does. Contrast that with the array of motors, glass discs,
photocells and valves of the original speaking clock back in 1936 - it took up most of the floor space of a small room!
organisations such as Network Rail, the BBC and London Weekend
Television have permanent feeds of the clock from BT into
their private internal phone systems so employees can check
the time without making an outside call. The timing of all
ITV television programmes is synchronised to TIM as well, so
when your local station goes over to ITN for the News at Ten,
this is done "at the third stroke". And perhaps the
strangest - and certainly longest distance - is calls to the British
speaking clock from the factory in Hong Kong
that which makes the handsets for the new VideoPlus VCR
programming system. The in-built clock is set to British
time, courtesy of BT's Timeline service.
by James Campbell (January 2001)
A direct feed existed to the
BBC. I remember in about 1983 visiting a BBC building on the
Embankment just round the corner from Westminster tube station, it was
Number 1 (can't remember the name of the
road). It was a half derelict building covered in pigeon sh*t, but on the second floor was the BBC Parliamentary
Recording Unit. It was linked via cables under the road
to the Houses of Commons and Lords. This was a place that
looked like a museum but was fully operational. The thing
that I found amusing was the fact that they recorded all
the material in mono on one track of the tape recorder
and recorded TIM on the other track as a quick time
reference. Because the pips were rather good at breaking
through to the other speech track, this particular TIM,
provided by BT, did not have any pips and was known by
the BBC as "seedless TIM".
What's left to see or
hear of the old clocks
Not a lot is the simple
answer. The Australian clock of 1954 used to be on display at
the Science Museum in London but after falling into disrepair was repaired
and is now in good working order and on display.
One of the original TIM clocks was preserved and was donated
by British Telecom to the British Horological
Institute's museum at Upton Hall near Newark, but this too is
not in working order.
People report having heard the Pat Simmons speaking clock
(thanks to TIM 2000) on the following numbers: (0870 765)
8081, (0845 092) 8081, 0845 124 9068 and (0131) 477 7676.
The above numbers may not be accurate so try 01352 838081 and 01286 868081.
Other Countries who used a speaking clock and have now
shut the service down:-
Australia - 2019
Ireland - 2018
In the year 2000 a project was devised for creating a compact
electronic speaking clock (with the Pat Simmons voice). Around 75 units were
sold (there are no plans to make any more).
Further resources on the WWW