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Telegraph Key - Elliott, Reversing, 1890s Object Reg. No: ST 022100

Summary:
Reversing telegraph key used for the transmission of signals in the electric telegraph system.

This type of key was used in conjunction with long submarine telegraph cables which distorted electrical signals so that the normal on-off pulses used in land telegraphy to mark the dots and dashes of Morse code would not work. Instead, the direction of flow of signal current was changed so that current flowing in one direction signalled a dot and in the other direction a dash. The reversing key used two separate keys, one for each direction of current flow.

At the receiving end the sequence of current pulses were displayed as a wavy line on a moving paper tape which could be interpreted by the operator .

Made by Elliott Bros, London. Used at Melbourne Observatory.
Description:
Two brass spring switches with ebonite knobs mounted on ebonite pillars. Cam adjustments for spring movement. All on ebonite base.
Acquisition Information:
Transfer from Melbourne Observatory, 1945
Discipline: Technology
Dimensions: 105 mm (Height), 110 mm (Width)

More information

Tagged with: morse keys, telegraph equipment, telegraphy
Themes this item is part of: Australia and the global telegraph network 1854-1902, The Australian telegraph network 1854-1877, Telegraphy Collection, Melbourne Observatory Collection, Information & Communication Collection, Positional Astronomy at Melbourne Observatory, Weights & Measures at Melbourne Observatory, Melbourne Observatory & Standard Time in Victoria, Astrographic Catalogue, Transits of Venus, 1874 & 1882, Buildings at Melbourne Observatory, Star Observations & Personal Equation, Meteorology at Melbourne Observatory, 1863-1908, Melbourne Observatory, 1863-1944, Geodetic Survey of Victoria, 1858-1872
Primary Classification: COMMUNICATIONS
Secondary Classification: Telegraphy
Tertiary Classification: components
Inscriptions: Base engraved: ELLIOTT BROS. / LONDON / 362
Maker: Elliott Bros, London, Middlesex, England, Great Britain
User: Melbourne Observatory, South Yarra, Victoria, Australia

Comments

Ron McMullen Posted on 13 Jul 2012 3:26 PM
This is a submarine cable testing key. A reversing key is a different key altogether. The tall standoffs reduce capacitance during sensitive measurements. Cams on each key arm allow the cable to be put to either voltage until a stable condition is reached as the cable charges up (behaving like a capacitor). Similar keys made by Walters,H.W.Sullivan and Gullette & Co..

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