Hall duplex telegraph relay
date: label: date made
content: ca 1875
name: label: maker
content: Farmer, Moses G.
label: maker
content: Hall, Thomas
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: This duplex relay was made by Thomas Hall of Boston and used in experiments by Moses Farmer. Duplex relays operated in a system designed to send two messages simultaneously over the same wire. Someone, Farmer himself perhaps, removed the electromagnet coils prior to the donation of the relay in 1899.
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.181947
label: catalog number
content: 181947
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: Measurements
content: overall: 4 in x 9 3/4 in x 5 3/4 in; 10.16 cm x 24.765 cm x 14.605 cm