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Telegraph Sounder - late 19th Century Object Reg. No: ST 022101

Summary:
Telegraph sounder used for the reception of telegraph messages transmitted by Morse code.

Telegraph signals were transmitted by an operator who depressd a key to complete an electric circuit and transmit current along the telegraph line. Releasing the key broke the circuit and cut off the current. Letters and numbers were represented by a sequence of short current pulses ('dots') and long current pulses ('dashes'), transmitted according to a defined code. The most widely used code was generally known as "Morse code".

At the receiving end of the telegraph line, the incoming current pulses passed to the receiving instrument, or 'sounder'. Two vertical wire coils were energised by the received pulses, causing the metal arm across the top of the coils to move up and down. The movement of the arm could be heard as a succession of metallic clicks. The interval between the clicks was short in response to the short current pulse representing a 'dot', or long in response to the long current pulse representing 'dash'. A skilled operator could interpret the succession of clicks as a pattern of dots and dashes and immediately decode the letters and numbers in the received message.

This sounder was used at Melbourne Observatory.
Description:
Two vertical wire coils and brass components on brass baseplate. Basepalte mounted on ebonite base. Two brass terminals on one end of ebonite base.
Acquisition Information:
Transfer from Melbourne Observatory, 1945
Discipline: Technology
Dimensions: 105 mm (Height), 70 mm (Width), 145 mm (Length)

More information

Tagged with: telegraphy
Themes this item is part of: 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: output
Inscriptions: Inscribed on top of brass baseplate:
"29"
Inscribed on side of ebonite base (twice):
"378"
User: Melbourne Observatory, South Yarra, Victoria, Australia

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