Williams-Farmer duplex telegraph patent model
date: label: Date made
content: 1875
name: label: associated person
content: Farmer, Moses G.
label: associated person
content: Woodman, Asa F.
label: maker
content: Charles Williams, Jr.
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 is the model that inventor Moses Farmer of Salem submitted along with the application that resulted in US Patent #160,581. Issued in 1875 the patent for an "improvement in Duplex-Telegraph Apparatus." A duplex telegraph sends two messages simultaneously through a single wire. Farmer found that on long lines a static charge built up and interfered with the operation of the circuit. He designed this apparatus with a relay, a duplex transmitter, a rheostat and special induction coils to counter that static charge. It is unclear how much of this device Farmer himself actually constructed since the relay bears the marking of Charles Williams, Jr., a noted telegraph and telephone maker in Boston.
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
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: EM.252638
label: catalog number
content: 252638
label: accession number
content: 49064
label: patent number
content: 160581
objectType: label: Object Name
content: relay
label: Object Name
content: telegraph relay
label: Object Type
content: Patent Model
label: Other Terms
content: telegraph relay; Telegraphy
physicalDescription: label: Physical Description
content: wood (overall material)
label: Physical Description
content: metal (overall material)
label: Physical Description
content: cloth (overall material)
label: Physical Description
content: ivory (overall material)
label: Measurements
content: overall: 5 in x 12 in x 12 in; 12.7 cm x 30.48 cm x 30.48 cm