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This page shows pictures taken by the GPO,
mainly in the mid to late 1920's. Included because they are clock related,
the buildings are of interest and some of the equipment fed GMT to the GPO
system.
The pictures cover both the Greenwich and Central
Telegraph Office (CTO)
sites.
The Post Office, in 1928, installed additional equipment
at Greenwich and the C.T.O. This equipment connected to the Rugby
Radio Station and was used to signal time for the International Time
Service.
Click here for an extract from an article on how GMT
is distributed to the Central Telegraph Office (CTO) and Rugby - in 1930.
Click here for more
information on the International Time Signal
Switching Panel used for International Time Service in
the Test Room of UK Central Telegraph Office,
London.
This was operated by the Greenwich time system via a 7 mile cable and this
Chronopher
then transmitted the signal to Rugby via 94 miles of cable
Picture dated 1928
Chronopher Control Clock - Central Telegraph Office
(CTO)
Picture dated 1924
Greenwich
Old buildings and Altazimuth House from new buildings (1929)
The Altazimuth Pavilion was built to house the new
Altazimuth Instrument proposed by Christie in 1892. It was constructed
between 1894 and 1896 to the design of William Crisp who also designed the
nearby New Physical Building (now known as the South Building). It was
grade II listed on 21 August 2002.
Greenwich - Altazimuth House
Picture dated 1929
Greenwich - Transit Circle Building
Note the raised roof section and open end panel in the centre of the
picture, above the portico
Picture taken 1929
Greenwich - Transit Circle Building
This is on the zero meridian and the telescope and collimators can be seen
between the buildings
Picture taken 1929
Greenwich - new Transit building
Picture taken 1929
Greenwich - Royal Obervatory
Picture taken 1929
Greenwich - Royal Observatory
South East dome
Picture taken 1929
Chronometer oven
Picture taken 1929
Chronometer room
Picture taken 1929
Greenwich - Mean Time Clocks
A free pendulum, a slave clock and a signal generator a housed in the
special container,
which keeps the temperature even and is free from vibration.
Picture taken 1935
Greenwich - Basement Clock Room
The Free Pendulum (made of Invar) is enclosed in an airtight case.
The Free Pendulum (a Shortt Clock) is connected to a Slave Clock which is a
standard Synchronome master clock.
This way of working reduces energy loss on the Free Pendulum with the slave
undertaking all the work.
Picture taken 1928
Greenwich - Sidereal Time Clock
Sidereal Standard time is the angle, measured along the celestial equator,
from the observer's meridian to the great circle that passes through the
March Equinox and both celestial poles, and is usually expressed in hours,
minutes, and seconds. Common time on a typical clock (mean Solar time)
measures a slightly longer cycle, accounting not only for Earth's axial
rotation but also for Earth's orbit around the Sun. Sidereal time is
used by Astronomers to easily point a telescope to the proper co-ordinates in
the night sky and is 23h 56m 04s of a solar day.
Greenwich - Riefler clock
Standard Mean Time Clock
Picture taken 1929
Greenwich - Tape Chronograph used for clock comparison
tests
Picture taken 1935
Greenwich - Time bench
Picture taken 1935
Greenwich - Winch and release mechanism for time-ball
Picture taken 1929
Greenwich, Flamsteed House - Time-ball
Picture taken 1928
The Time-ball was first used in 1833 and is still in use today. It
rises daily at 12.58 and drops at 13.00 exactly
Rugby - Signal clock room
Picture taken 1928
Greenwich Observatory Signal clock room
Special apparatus used by the International time service
Picture taken 1928
Greenwich Observatory
Mechanism of the special signal transmitter used on the International Time
Service
Picture taken 1928
Greenwich Observatory
Spare Transmitter Clock for the International Time Service
Picture taken 1928
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