Elisha Gray patent model telegraph repeater

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Telegraph repeaters amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, limiting the distance a message could travel. Repeaters remedied that problem by detecting a weak signal and using a local power source to re-energize and re-transmit the signal down the line.
This working model was submitted to the U.S. Patent Office by inventor Elisha Gray of Chicago along with his patent application. On 16 May 1871, he received patent #114938 for his "Improvement in Telegraph-Repeaters." Gray's idea, called a "shunt repeater," transferred or "shunted" some of the electrical current to an extra pair of small electromagnets to allow for automatic operation of the repeater. Our records also associate this object with telegraph inventor Charles Haskins although the association is unclear. While Haskins did patent his own repeater whose action was described at the time as "similar to Gray's," patent 114938 was issued to Gray alone and was not assigned to anyone else.
Currently not on view
date made
Gray, Elisha
Physical Description
wood (overall material)
metal (overall material)
rubber (overall material)
cloth (overall material)
overall: 4 1/2 in x 13 in; 11.43 cm x 33.02 cm
ID Number
catalog number
accession number
patent number
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Work and Industry: Electricity
Telegraph Relays & Repeaters
Data Source
National Museum of American History


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