Bunnell main-line telegraph relay
name: label: maker
content: J. H. Bunnell & Co.
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 by J. H. Bunnell & Company 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 was used in experiments by the noted electrical inventor Moses Farmer.
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 Sarah J. Farmer
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: EM.181946
label: catalog number
content: 181946
label: accession number
content: 2015.0173
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: plastic (overall material)
label: Measurements
content: overall: 3 1/2 in x 8 1/4 in x 4 1/2 in; 8.89 cm x 20.955 cm x 11.43 cm