Bell hard rubber receiver/ transmitter
Date: 1879
Inventory Number: 8011
Classification: Telephone
Dimensions:18.1 × 7.1 × 7.1 cm (7 1/8 × 2 13/16 × 2 13/16 in.)
DescriptionA Bell speaking telephone receiver/transmitter made of hard rubber, of the type known as a "butterstamp" style. The instrument is slightly larger at the terminal end, which has two binding posts with Phillips-head ends. The wired end has a Philips-head screw in the center, and an eyehook. The other end is flared and contains a screw-on base with integral mouthpiece/earpiece with a concave dish shape and a center opening.
Inside, a hexagonal permanent bar magnet is placed opposite a vibrating plate or diaphragm made of ferrotype iron. The diaphragm acts as an armature to the magnet, and when it moves, changes the magnetic field in which the coil fixed at the end of the magnet is placed. Speaking into the transmitter causes the diaphragm to vibrate, and excite currents in the coil.
Around the opening is printed: inscribed around end, "Property of National Bell Telephone Co / PAT. MARCH 7-76 & JAN. 30-77 / A 14965 ."
The receivers were manufactured for use with the "coffin" style magneto telephone produced for the Bell Telephone Company by Charles Williams, beginning in 1878.
This style of telephone used a switchhook, patented in 1877 by Hilbourne Roosevelt, an organ manufacturer. The switchook allowed the user to connect by lifting the receiver, rather than by activating a switch.
Signedsigned: THE NATIONAL BELL TELEPHONE CO.
Inscribedinscribed around end: Property of National Bell Telephone Co;
stamped on handle: PAT. MARCH 7-76 & JAN. 30-77;
stamped on stem below terminals: A14965
FunctionConversion of sound into electric signals for transmission over a distance and conversion of electric signals into sound for output by telephone
Historical AttributesNational Bell formed March 20, 1879; superseded by American Bell March 19, 1880.
ProvenanceJefferson Laboratory, Physics Department, Harvard University
Published ReferencesThis instrument is described in:
Thomas G. Hedberg, "Catalogue: Telephones, Phonographs and Related Instruments in The Collection of Historical Scientific Instruments at Harvard University." William Andrewes, Project Director (unpublished manuscript, President and Fellows of Harvard College and Thomas G. Hedberg, 1989. Fifth Draft), pp. 27-28.