The phonic Motors of the Greenwich Time Service


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The phonic motor supplied with the Observatory's first Quartz Clock

The observatory's first quartz clock, Q3, was built by the National Physical Laborator and delivered to the Observatory in early 1939. designed to give impulses at one-hundredth of a second, one-tenth of a second and one second intervals. In his 1940 Report to the Board of Visitors, Spencer Jones recorded 'The phonic motor has proved to be the most troublesome part of the equipment and it is apparent that the clock is not giving as good a performance as it should'.


The phonic motors supplied for the Quartz Clocks A1, B1 & B2 installed at Abinger and Edinburgh

The Quartz Clocks A1, B1 & B2 were supplied by the General Post Office and installed at Abinger and Edinburgh in February 1944 - A1 being at Edinburgh and B1 & B2 being at Abinger. In his 1943 Report, Spencer Jones recorded 'These clocks are now under construction by the Post Office Radio Department and it is proposed to equip two of them, one for each time service station, with phonic motors carrying gearing to enable them to be used as rhythmic signal transmitters.' going on to say, the present transmitting clocks, which are of the slave clock type [the Shortts], suffer from many defects such as irregularity of contacts and wandering of phase and their replacement is a matter of urgency. The second clock at Abinger was provoded with a motor with a simple once-per second contact.


Phonic motors at the Science Museum and in the BHI collection at Upton Hall

The following two phonic motors form part of Object ID: 1990-303 Pt1 at the Science Museum, which is described as 'Representative sample of the equipment used for maintaining the Greenwich Time Service from about 1965 to 1990 comprising six racks of electronic equipment, two end doors, five rear doors, three covers, printer and sign'. The object ID suggests that they were acquired in 1990 when the Observatory vacated its site at Herstmonceux.

  • Transmitting Motor No 3 Royal Greenwich Observatory
  • Solar-Sidereal Frequency Tranformer No2 Royal Greenwich Observatory

The BHI collection at Upton Hall has a similar, but not identical unit of six racks which also contain a Transmitting Motor and a Solar Solar-Sidereal Frequency Tranformer.


Further Reading

On the mean solar to mean sidereal gear ratio. Roy Tucker, The Observatory, Vol. 67, p. 185-186 (1947)