Western Union type 4-B main-line telegraph relay
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 type 4-B relay was common in the Western Union system in the early 20th century. The unit bears an inspection stamp "N.Y.R.S. 5 27" indicating that it was serviced at Western Union's New York Repair Shop in May 1927.
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.331667
label: accession number
content: 294351
label: catalog number
content: 331667
label: collector/donor number
content: 04-19
objectType: label: Object Name
content: single current relay
label: Object Name
content: telegraph relay
physicalDescription: label: Physical Description
content: grass (overall material)
label: Physical Description
content: steel (overall material)
label: Physical Description
content: plastic (overall material)
label: Physical Description
content: iron (overall material)
label: Physical Description
content: slate (overall material)
label: Measurements
content: overall: 3 3/4 in x 8 in x 4 3/4 in; 9.525 cm x 20.32 cm x 12.065 cm