Gray telegraph relay patent model
date: label: date made
content: 1867
name: label: maker
content: Gray, Elisha
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 relay was constructed early in 1867 by noted electrical inventor Elisha Gray to accompany a patent application. He received US Patent 69,424 later that year for an improved telegraph relay. Gray's idea was to use a second set of electromagnet coils rather than a spring to retract the armature after a signal pulse. He wrote that the pulse's strength could vary so much that a relay's spring needed constant adjustment. His design compensated automatically for the variation in pulse strength.
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
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content: Telegraph Relays & Repeaters
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: EM.308870
label: catalog number
content: 308870
label: accession number
content: 89797
label: patent number
content: 69424
objectType: label: Object Name
content: relay
label: Object Name
content: telegraph relay
label: Object Type
content: Patent Model
physicalDescription: label: Physical Description
content: wood (overall material)
label: Physical Description
content: brass (overall material)
label: Physical Description
content: plastic (overall material)
label: Physical Description
content: cloth (overall material)
label: Measurements
content: overall: 4 1/2 in x 11 1/2 in x 5 3/8 in; 11.43 cm x 29.21 cm x 13.6525 cm