Scientific American Supplement, No. 530, February 27, 1886Various
Science
Scientific American Supplement, No. 530, February 27, 1886
Various
Science -- Periodicals
It is certain that this question will acquire prominence as soon as a
system of local government has been adopted, in which the wants of the
several communities have full opportunity of asserting themselves, and in
which each local authority shall have power to decide on those measures
which are essential to the development of the resources of its own
district, without interference from a centralized bureaucracy.
* * * * *
ON THE THEORY OF THE ELECTRO-MAGNETIC TELEPHONE TRANSMITTER.
By E. MERCADIER.
[Footnote: Note presented to the Academy of Sciences, Oct. 19, 1885.]
The first point to be studied in this theory is the _role_ performed by
the iron or steel diaphragm of the telephone, both as regards the nature
of the movements that it effects through elasticity and the conversion of
mechanical into magnetic energy as a result of its motions.
I. When we produce simple or complex vibratory motions in the air in
front of the diaphragm, like those that result from articulate speech,
either the fundamental and harmonic sounds of the diaphragm are not
produced, or else they play but a secondary _role_.
(1.) In fact, diaphragms are never set in vibration, as is supposed, when
we desire to determine the series of harmonics and nodal lines, since we
do not leave them to themselves until they have been set in motion, and
we do not allow a free play to the action of elastic forces; in a word,
the vibrations that they are capable of effecting are constantly _forced_
ones.
(2.) When a disk is set into a groove, and its edges are fixed, theory
indicates that the first harmonics of the free disk should only rise a
little. Let us take steel disks 4 inches in diameter and but 0.08 inch in
thickness, and of which the fundamental sound in a free state is about
_ut_{5}_, and which the setting only further increases. It is impossible
to see how this fundamental and the harmonics can be set in play when a
continuous series of sounds or accords below _ut_{5}_, are produced
before the disk; and yet these sounds are produced perfectly (with feeble
intensity, it is true, in an ordinary telephone) with their pitch and
quality. They produce, then, in the transmitting diaphragm other motions
than those of the fundamental sound and of its peculiar harmonics.
Public-domain text, read in full here on John Shaqi.
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