main-line telegraph relay
date: label: date made
content: ca 1870
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: “Main line” relays like this unit were one of the most common types of relay and were typically made with a resistance of 150 ohms. As the name suggests, main line relays served on major intercity circuits several hundred miles long. This unit has a 122 ohm rating indicating its use on a somewhat shorter line than usual. We know a little bit more than usual about the past history of this unit, something called "provenance" in museum-speak. The relay came to the Smithsonian from the former Western Union Museum in 1972. There's a business card from J. F. Calahan, Manager, Western Union Co., Parkersburg, WV taped to bottom. The curator at the WU Museum wrote on the card: "Rec'd Feb. 24, 1954 from J.F.C. / Donated by Carl B. Wetzel / Eureka Pipe Lines Co. / 218 - 5th St., Parkersburg." Where Mr. Wetzel found the relay remains a mystery.
label: Location
content: Currently not on view
setName: label: See more items in
content: Work and Industry: Electricity
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content: Communications
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content: Telegraph Relays & Repeaters
creditLine: label: Credit Line
content: from Western Union Corporation
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: EM.331403
label: accession number
content: 294351
label: catalog number
content: 331403
label: collector/donor number
content: 100-019
objectType: label: Object Name
content: relay
label: Object Name
content: telegraph relay
physicalDescription: label: Physical Description
content: wood (overall material)
label: Physical Description
content: metal (overall material)
label: Physical Description
content: brass (overall material)
label: Physical Description
content: plastic (overall material)
label: Measurements
content: overall: 3 3/4 in x 8 1/2 in x 4 1/2 in; 9.525 cm x 21.59 cm x 11.43 cm