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1937 - for practice, the students can hear themselves through the earphones and be inaudible to others, except the instructor

HAMMOND TONE-WHEEL

E&MP 88.014

Music Recording - Electronic

June 1937

Close-up showing a Hammond tone-wheel.

The wheel has convolutions on the rim and in operation it revolves close to the magnet such as shown in the photo.

In the coil of the magnet is set up a tiny alternating current corresponding to the number of convolutions that pass through the magnetic field in a second.

Thus 440 vibrations would give A on the international music scale.


Original Caption by Science Service
© PHOTOGRAPHIC ILLUSTRATIONS INC CHICAGO ILLINOIS



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