Clark telegraph relay
date: label: date made
content: 1846
name: label: maker
content: Clark, James J.
notes: label: Description
content: Telegraph relays 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, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
label: Description
content: George C. Maynard, the curator who collected this piece in 1897, showed this and a similar relay to Dr. James J. Clark who, “examined these relays and said they were made by him about 1846 in Philadelphia. [They] represent the first big step in relay construction, after the 'big magnets' first used by [Samuel] Morse. They were originally [mounted] in a box with the adjusting screws projecting. The Clarks (J. J. and his father) made and sold many of these relays. [The Clarks] supplied [Henry] O'Rielly and all the southern lines."
label: Location
content: Currently not on view
setName: label: See more items in
content: Work and Industry: Electricity
label: See more items in
content: Communications
label: See more items in
content: Telegraph Relays & Repeaters
creditLine: label: Credit Line
content: from Western Union Telegraph Co.
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: EM.181422
label: catalog number
content: 181422
label: accession number
content: 31652
objectType: label: Object Name
content: relay
label: Object Name
content: telegraph relay
physicalDescription: label: Physical Description
content: wood (overall material)
label: Physical Description
content: brass (overall material)
label: Physical Description
content: steel (overall material)
label: Physical Description
content: ivory (overall material)
label: Physical Description
content: cloth (overall material)
label: Physical Description
content: copper (overall material)
label: Measurements
content: overall: 6 in x 7 3/4 in x 3 7/8 in; 15.24 cm x 19.685 cm x 9.8425 cm