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Catalog Data

Inventor:
Bell, Alexander Graham  Search this
Maker:
Bell, Alexander Graham  Search this
Physical Description:
wood (parts material)
iron (magnet material)
brass (hardware material)
iron (diaphram material)
mica (insulator 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
Object Name:
telephone
box telephone
Other Terms:
box telephone; Telephones; Transmitter/Receiver
Associated Place:
United States: Massachusetts, Salem
United States: Massachusetts, Boston
Date made:
1876
Used in a demonstration:
1876
Description:
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.
Location:
Currently not on view
Subject:
Telephone  Search this
Magnet  Search this
Credit Line:
from American Telephone & Telegraph Company
ID Number:
EM.308214
Catalog number:
308214
Accession number:
70856
See more items in:
Work and Industry: Electricity
Communications
American Stories exhibit
Data Source:
National Museum of American History
GUID:
http://n2t.net/ark:/65665/ng49ca746ab-f6ef-704b-e053-15f76fa0b4fa
EDAN-URL:
edanmdm:nmah_704159