Telephone - Introduction
Telephony is the art of reproducing sounds at a distance from their source. The term was first used before Reis of Friedrichsdorf, in a lecture delivered before the Physical Society of Frankfort in 1861. [Footnote 127-1] But, although this lecture and Reis subsequent work received considerable notice, little progress was made until the subject was taken up between 1874 and 1876 by Alexander Graham Bell, a native of Edinburgh, then resident in Boston, Mass. Bell, like Reis, employed electricity for the reproduction of sounds ;but he attacked the problem in a totally different manner. This will be better understood if we consider shortly on what the chief characteristics of sound depend (compare ACOUSTICS).
The sensation of sound is produced by rapid fluctuations in the pressure of the atmosphere on the tympanum of the ear. If the fluctuations are irregular and non-periodic, the sound is called a noise ; if they are cyclic and follow a regular and sufficiently rapid periodic law, the sound is musical. In connexion with the present subject it is important to notice the three characteristics of a musical sound, namely, pitch, loudness, and quality. The pitch of a musical sound depends on the number of cycles passed through by the fluctuations of the pressure per unit of time ; the loudness depends on the amount or the amplitude of the fluctuation in each cycle ; they quality depends on the form or the nature of the fluctuation in each cycle. The necessary condition for a successful system of telephony is the ability to reproduce these characteristics.
127-1 "Ueber Telephonie durch den galvanischen Strom," in Jahresber. d. physikalischen Vereins zu Frankfurt am Main, 1860-61, p. 57.
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Telephone - Table of Contents