Alexander Graham Bell's Large Box Telephone
date: label: date made
content: 1876
label: used in a demonstration
content: 1876
name: label: inventor
content: Bell, Alexander Graham
label: maker
content: Bell, Alexander Graham
notes: label: Description
content: One of two telephones used by Alexander Graham Bell in a demonstration that took place between Boston and Salem, Massachusetts on November 26, 1876. Critical features are the iron diaphragm (seen as a black circular disc mounted on the vertical wooden support), two electromagnets (seen in white, facing the diaphragm) and a horseshoe permanent magnet (lying horizontal, pressed against the electromagnets).
label: Description
content: When used as a transmitter, sound waves at the mouthpiece cause the diaphragm to move, inducing a fluctuating current in the electromagnets. This current is conducted over wires to a similar instrument, acting as a receiver. There, the fluctuating current in the electromagnets causes the diaphragm to move, producing air vibrations that can be heard by the ear. This was a marginal arrangement, but it worked well enough to be employed in the first commercial services in 1877. The magneto receiver continued to be used, but the transmitters were soon replaced by a carbon variable-resistance device designed by Francis Blake and based on a principle patented by Thomas Edison.
label: Location
content: Currently not on view
place: label: Associated Place
content: United States: Massachusetts, Salem
label: Associated Place
content: United States: Massachusetts, Boston
topic: label: Subject
content: Telephone
label: Subject
content: Magnet
setName: label: See more items in
content: Work and Industry: Electricity
label: See more items in
content: Communications
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content: American Stories exhibit
creditLine: label: Credit Line
content: from American Telephone & Telegraph Company
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: EM.308214
label: catalog number
content: 308214
label: accession number
content: 70856
objectType: label: Object Name
content: telephone
label: Object Name
content: box telephone
label: Other Terms
content: box telephone; Telephones; Transmitter/Receiver
physicalDescription: label: Physical Description
content: wood (parts material)
label: Physical Description
content: iron (magnet material)
label: Physical Description
content: brass (hardware material)
label: Physical Description
content: iron (diaphram material)
label: Physical Description
content: mica (insulator material)
label: Measurements
content: overall: 6 1/4 in x 7 1/2 in x 12 1/2 in; 15.875 cm x 19.05 cm x 31.75 cm