Bunnell telegraph repeater patent model

Description
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 model was submitted to the U.S. Patent Office by inventor Jesse Bunnell of New York City along with his patent application. On 26 January 1868, he received patent #73774 for his "Improvement in Telegraph-Repeaters." In their 1877 review of telegraph equipment, Charles Davis and Frank Rae reported that in Bunnell's repeater, “the arrangement of the main circuits ... is exactly like that of an ordinary button repeater.” However, instead of a person operating the lever to engage the repeater, the switching was made automatic thru the use of “two governor magnets.” The governor magnets were wound with a much finer wire than that used in the sounders so the resistance, and hence the magnetic field, differed between the two and enabled the automatic switching to operate.
Location
Currently not on view
Object Name
telegraph set
telegraph relay
telegraph repeater
date made
1867
maker
J. H. Bunnell & Co.
Physical Description
brass (overall material)
wood (overall material)
cloth (overall material)
steel (overall material)
copper (overall material)
Measurements
overall: 3 1/4 in x 12 in x 11 7/8 in; 8.255 cm x 30.48 cm x 30.1625 cm
ID Number
EM*251258
catalog number
251258
accession number
48865
patent number
73774
subject
Communications
Telegraph Relays & Repeaters
See more items in
Work and Industry: Electricity
Telegraph Relays & Repeaters
Data Source
National Museum of American History, Kenneth E. Behring Center
Additional Media

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