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Inventory no. 68206 - Former Display Label

MODEL OF AN IMPULSE DIAL
c.1850

Signed: "WATKINS & HILL 5 CHARING CROSS LONDON". Inscribed: "WHEATSTONES ELECTRO MAGNETIC CLOCK".
Overall height 345mm.
Movement of brass and steel; painted dial 0-60, polished mahogany case. When energized by an electric impulse from a master-clock, or perhaps in this case from a switch, the electro-magnet attracts an armature. The movement of the armature towards the electro-magnet actuates an escapement causing the single hand to move from one division of the dial to the next. The release of the armature, on the cessation of the impulse, moves the hand a further division. The cycle of movement is then repeated.
This model demonstrates the principle of the slave clock or impulse dial. Alexander Bain who marketed his first electrically-driven pendulum clock in 1840, the following year patented a system in which a large number of impulse dials could be connected to a single master clock. A long case electric master clock by this maker is exhibited in the stairwell display area. Wheatstone devised several impulse dial mechanisms and also a master clock.
Most of the early workers in telegraphy were also interested in electrical horology. Many of the mechanisms had applications in both fields, and this Museum has another similar instrument but with the numerals on the dial replaced by letters. The expansion of the nineteenth-century railway network and international trade relied on the rapid transmission of information and on the accurate and uniform distribution of time.

[C. L. 11]
Transferred from the Clarendon Laboratory.

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