Telegraph Key
date: label: date made
content: ca 1868
name: label: maker
content: Charles Williams, Jr.
notes: label: Description (Brief)
content: Telegraph keys are electrical switches used to send coded messages that travel as a series of electrical pulses through a wire. Due to special difficulties in sending pulses through long underwater cables, so-called double-current keys were used. Instead of the short dots and long dashes of land-line telegraphs, submarine telegraphs sent positive pulses and negative pulses that made the receiver move right or left. The operator pressed one lever on the key to send a positive pulse and another to send a negative pulse. The code consisted of the sequence of left and right movements recorded on a paper tape.
label: Description (Brief)
content: Curator George Maynard, who collected this key in 1897, reported: this key was "used to determine differences of longitude between principal meridians of the British Islands and the principal meridians of the United States by means of telegraphic cables from Brest, France, to Duxbury, Mass., to Cambridge, to Washington, D.C., 1869-1872."
label: Description (Brief)
content: Two keys each with ivory knob mounted on an oval rubber base. Marked once on each key arm: "C. Williams, Jr. Boston". "
label: Description (Brief)
content: Note in accession file reads: "Atlantic Cable Signal Key. For exchange of longitude signals between European and American stations. US Cast and Geodetic Survey. 1896-1870 and 1872.
label: Description (Brief)
content: "This key is arranged so that two circuits pass through it; one of these is the Atlantic Cable circuit; the other the local circuit which connects with the recording chronograph of the astronomical station.
label: Description (Brief)
content: "A series of signals having been agreed upon, the observer at the eastern stations (Brest) charges or discharges the cable at fixed intervals; the instant of charge or discharge is then noted by the observer at the western station (St. Pierre or Duxbury) and recorded upon his chronograph. On the completion of this series, the observer at the western station would send positive or negative signals through the cable in the order already arranged; these are noted by the eastern observer upon his chronograph.
label: Description (Brief)
content: "It was found that the signals given by the discharge of the cable produced a much quicker and more easily noted deflection of the ray of light from the cable mirror; hence these signals were preferred by the observers; and the sets of exchanges arranged accordingly.
label: Description (Brief)
content: "See Smithsonian Institution Contribution to Knowledge, No. 223 by Professor Joseph Lovering of Harvard College, and USC&G Survey Report for 1874, Appendix 18, by J. E. Hilgard. (Read from Edward Goodfellow, Dec. 11, 1897, G.C.M.)"
label: Description (Brief)
content: A second note reads: "Key used by Edward Goodfellow, Assistant, US Coast & Geodetic Survey for sending and receiving longitude signals through the Atlantic Cable stations at Duxbury and St. Pierre."
label: Location
content: Currently not on view
setName: label: See more items in
content: Work and Industry: Electricity
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content: Telegraph Keys
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content: Communications
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: EM.181671
label: catalog number
content: 181671
label: accession number
content: 32985
objectType: label: Object Name
content: telegraph key
label: Object Name
content: cable key
label: Object Name
content: submarine telegraph key
physicalDescription: label: Physical Description
content: wood (overall material)
label: Physical Description
content: rubber (overall material)
label: Physical Description
content: ivory (overall material)
label: Physical Description
content: brass (overall material)
label: Measurements
content: overall: 2 1/2 in x 6 in x 7 3/4 in; 6.35 cm x 15.24 cm x 19.685 cm