main-line telegraph 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 made/used by [name] 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 relay has a 170 ohms rating, somewhat higher than usual.
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 Corporation
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: EM.331766
label: catalog number
content: 331766
label: accession number
content: 294351
label: collector/donor number
content: 100-014
objectType: label: Object Name
content: telegraph relay
physicalDescription: label: Physical Description
content: brass (overall material)
label: Physical Description
content: wood (overall material)
label: Physical Description
content: steel (overall material)
label: Physical Description
content: plastic (overall material)
label: Measurements
content: overall: 3 3/4 in x 9 in x 4 1/4 in; 9.525 cm x 22.86 cm x 10.795 cm