In 1861, Reis, of Germany, came into notice as the inventor of a telephone which transmitted sound very clearly, but failed to reproduce syllabified speech. However, the principle and shape of his transmitter and receiver were accepted by those who followed him. Two men now came upon the scene who had reached the conclusion already arrived at by Drawbaugh, and who became rivals over his head for the honor and profit of an invention by means of which the quality of the voice in speaking could be transmitted. These two were Elisha Gray, of Chicago, and Alexander Graham Bell, of Boston. Their respective devices seem to have been akin, and to have been presented to the patent office almost simultaneously; so nearly so, at least, as to make them a part of that long, costly, and acrimonious legal contention over priority of invention which did not end till 1887.
Both Bell and Gray reached the conclusion that the transmission of articulate speech was impossible unless they could produce electrical undulations corresponding exactly with the vibrations of the air or sound waves. They brought this similarity about by introducing a variable resistance into the electric current by means of an interposing liquid, just as Drawbaugh had done years before with his tumbler of powdered charcoal. Bell exhibited his instrument with comparative success at the Centennial Exhibition in 1876 in Philadelphia; but much had yet to be done to perfect a telephone of real commercial value.
The years 1877–78 were years of great activity among electricians, whose prime object was to perfect a telephone transmitter and receiver, by means of whose mutual operations at opposite ends of a circuit all the modulations of speech could be preserved and passed. To this end Berliner introduced into a transmitter or sender the then well-known principle of the microphone (Gr. mikros, small, phone, sound), which magnified the faint sounds by the variation in electrical resistance, caused by variation of pressure at loose contact between two metal points or electrodes. Edison quickly followed with a similar transmitter or sender, in which one of the electrodes was of soft carbon, the other of metal. Then came (1878) Hughes and Blake with senders, in which both of the electrodes were of hard carbon. Subsequently came other and rapid modifications of the sender, both in the United States and Europe, till the form of telephone now in popular use was arrived at, and which, strange to say, is, in its method of securing the necessary variable resistance in the circuit, quite like that employed by Mr. Drawbaugh; to wit, the introduction of fine carbon granules into a small metal cup just behind the vibrating diaphragm or disk of the sender. The circuit goes into the diaphragm in front, passing through the carbon granules and out through the back of the instrument. The action of talking into the sender causes the granules to be agitated, thus opening and closing the circuit and producing the conditions necessary to the transmission of articulate speech. The diaphragm or disk is the very thin covering of the cup containing the granules. It is sometimes made of carbon, but generally of hard metal, as steel. On being struck by the sound waves of the voice, it vibrates to correspond. The same vibrations are reproduced in the receiver at the opposite end of the circuit, and thus one listens to the phenomenon of transmitted human speech. The current for telephonic purposes is furnished by one or more batteries or cells, whose effect is heightened by the presence of an induction coil. The tendency now is to make “bipolars”—two contacts at the diaphragm—in place of a single contact. This style is becoming more in vogue in order to meet the demands of long-distance work. To each telephone is attached a generator or device for ringing a little bell as a signal that some one wishes to communicate. To such perfection have telephones been brought that it is quite possible to converse intelligibly at the distance of a thousand miles, with a less satisfactory service at twice or thrice that distance. The possibilities of clear speech-transmission at indefinite distance are without measure. Like the telegraph, the telephone has opened an immense and profitable industry, involving hundreds of millions of dollars. At the end of the century it is, unfortunately, monopolistic; but the time is near when a reasonable charge for service will enable every business house to communicate with its customers, and when even the remote corners of counties will be brought into touch with their capitals and with one another. Along the lines of civilizing contact the telephone fairly divides the wonders of the century with the telegraph, while for intimate intellectual communication it is a triumph of genius without parallel. It is the dispenser of speech in city, town, and village; in factory and mine, in army and navy; throughout government departments; and in Budapest, Hungary, it is a purveyor of general news, like the newspaper, for the “Telephone Gazette” of that city has a list of regular subscribers, to whom it transmits, at private houses, clubs, cafes, restaurants, and public buildings, its editorials, telegrams, local news, and advertisements.
A very natural outgrowth of the telephone was that curious invention known as the phonograph (Gr. phone, sound, and graphein, to write). It is not only an instrument for writing or preserving sound, but for reproducing it. As a simple recorder of sound, it was an instrument dating as far back as 1807, when Dr. Young showed how a tuning-fork might be made to trace a record of its own vibrations. But Young’s thought had to go through more than half a century of slow evolution before the modern phonograph was reached; for in the phonautograph of Scott, the logographs of Barlow and Blake, and the various other attempts up to 1877 to make and preserve tracings of speech, there were no successful means of reproducing speech from those tracings hit upon.
A GRAPHOPHONE.
In that year (1877), Edison, in striving to make a self-recording telephone by connecting with its diaphragm or disk a stylus or metal point which would record its vibrations upon a strip of tinfoil, accidentally reversed the motion of the tinfoil so that the tracings upon it affected the stylus or tracing-point in an opposite direction. To his surprise, he found that this reverse motion of the tinfoil, tickling, as it were, the stylus oppositely, reproduced the sounds which had at first agitated the diaphragm. It was but a step now to the production of his matured phonograph in 1878. He made a cylinder with a grooved surface, over which he spread tinfoil. A stylus or fine metal point was made to rest upon the tinfoil, so as to produce a tracing in it, following the grooves in the cylinder when the latter was made to revolve. This stylus was connected with the diaphragm of an ordinary telephone transmitter. When one spoke into the transmitter, that is, set the diaphragm to vibrating, the stylus impressed the vibratory motions of the diaphragm, or, in other words, the waves of the exciting sound, in light indentations upon the tinfoil. In order to reproduce the sounds thus registered in the tinfoil of the cylinder, it was made to revolve in an opposite direction under the point of the stylus, and as the stylus was now affected by precisely the same indentations it had first made in the tinfoil, it carried the identical vibrations it had recorded back to the diaphragm of the telephone, and thus reproduced in audible form the speech that had at first set the diaphragm to vibrating. The speech thus reproduced was that of the original speaker in pitch and quality. Ingenious and wonderful as Edison’s machine was, it was susceptible of improvement, and soon Bell and others came forward with a phonograph in which the recording cylinder was covered with a hardened wax. This was called the graphophone. Again, Berliner improved upon the phonograph by using for his tracing surface a horizontal disk of zinc covered with wax. By chemical treatment, the tracings made in the wax were etched into the zinc, and thus made permanent. Edison made further and ingenious improvements upon his phonograph by attaching hearing tubes for the ear to the sound receiver, and by the employment of an electric motor to revolve the wax cylinder. By the attachment of enlarged trumpets and other devices, every form of modern phonograph has been rendered capable of reproducing in great perfection the various sounds of speech, song, and instrument, and has become a most interesting source of entertainment.
V. DYNAMO AND MOTOR.
Dynamo is from the Greek dunamis, meaning power. Motor is from the Latin motus, or moveo, to move. Dynamo is the every-day term applied to the dynamo-electric machine. Motor is the every-day term applied to the electric motor. The dynamo and motor are quite alike in principle of construction, yet direct opposites in object and effect. Perhaps it might be well to designate both as dynamo-electric machines, and to say that, when such machine is used for the conversion of mechanical energy or power of any kind into electrical energy or power, it is a dynamo. When a reverse result is sought, that is, when electrical energy or power is to be converted into mechanical energy or power, the machine that is used is a motor. In practical use for most purposes they are brought into coöperation, the dynamo being at one end of an electric system, making and sending forth electricity, the motor being at the other end, taking up such electricity and running machinery with it. Both machines were epoch-making in the midst of a wondrous century, and both were results of those marvelous evolutions in electrical science which characterized the earlier years of the century.