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Alexander Graham Bell's Large Box Telephone | by national museum of american history
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Alexander Graham Bell's Large Box Telephone

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).

 

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.

 

Object Name

telephone

 

box telephone

 

date made

1876

 

used in a demonstration

1876

 

patentor

Edison, Thomas A.

 

inventor

Bell, Alexander Graham

 

Blake, Jr., Francis

 

maker

Bell, Alexander Graham

 

Physical Description

wood (parts material)

 

iron (magnet material)

 

brass (hardware material)

 

mica (diaphram material)

 

Measurements

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

 

Associated Place

United States: Massachusetts, Salem

 

United States: Massachusetts, Boston

 

ID Number

EM*308214

 

catalog number

308214

 

accession number

70856

 

subject

Telephone

 

Magnet

 

Communications

 

American Stories exhibit

 

See more items in

Work and Industry: Electricity

 

American Stories exhibit

 

Exhibition

American Stories

 

Data Source

National Museum of American History, Kenneth E. Behring Center

 

Credit Line

from American Telephone & Telegraph Company

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Uploaded on March 1, 2013