The History of the Telephone circa 1895

[as reprinted from Cassier’s magazine v. 8 May-Oct. 1895. Article by W. Clyde Jones]

The telephone has become such a commonplace appliance of modern life that one seldom stops to think what a wonderful instrument it is, nor yet what a great factor it has be- come in everyday life. Like other important inventions, it is the outcome of a long evolutionary process.

It was in 1819 that Oersted, a professor in the University of Copenhagen, while lecturing to his class, discovered that a magnetic needle, when held in the vicinity of a wire traversed by an electric current, was caused to assume a position at right angles to the axis of the wire. This experiment, though simple of performance, was a revelation to the scientific world, and confirmed the long-standing suspicion that electricity and magnetism were, in some mysterious manner, related. This was the spark that inflamed the minds of scientific men and led to the unraveling of the apparent mysteries of electro-magnetic action and the founding of the laws of electro-magnetism, to which we are, in such a great measure, indebted for the industrial development of the electrical arts.

Oersted had informed the world that there was a relation between electricity and magnetism, but it remained for Sturgeon, in 1825, to point out that there was not only a relation, but that electricity was even convertible into magnetism. He had encircled a bar of soft iron with a helix of wire and noted that upon the passage of an electric current through the helix the soft iron bar assumed the properties of a magnet. Here was the germ that was afterward developed into the telegraph and the telephone. With the electro-magnet the minds of men naturally turned to the transmission of intelligence to a distance, and in the years immediately following Sturgeon’s experiment we find the greatest scientific minds busily engaged with the problem. Neither the laws of the electro-magnet nor the laws governing the passage of a current along a wire, since so admirably expressed by Ohm, were at this time known, and the rapid falling away of the force of the current with increased distance led to the belief that an electro-magnetic telegraph would never be possible. Indeed, in 1829, Professor Barlow, of England, perhaps the foremost scientist of his day, after making an exhaustive study of the problem, published a demonstration, considered at the time conclusive, showing that it would be absolutely impossible to transmit intelligence to a distance by means of the electro-magnet.

But soon the dormant hope was again aroused by the publication of the researches of Joseph Henry, who had so thoroughly investigated the laws of the electro-magnet that no discoveries, except of minor importance, have resulted from later investigation; in fact, the electro-magnet as Henry knew it in 1830 is the electro-magnet as we know it to-day.

Ever since Sturgeon had converted electricity into magnetism, the question ever uppermost in scientific minds was whether magnetism might not, in turn, be converted into electricity. In 1831, Henry and Faraday discovered that magnetism was, in fact, convertible into electricity, and was effected by varying the magnetic field threading a looped conductor. By this discovery, which has rendered illustrious the names of two great men, the world acquired information concerning the laws of electro-magnetism and the mutual convertibility of the two mysterious forces that immediately removed electrical science from the domain of the purely theoretical and experimental and gave it a place in the industrial world.

The time was ripe for the development of the electric telegraph, and in the early 30′ s Samuel F. B. Morse had conceived the electric telegraph, which, toward the end of the decade, assumed practical form. With Sturgeon’s electro-magnet placed at the distant end of the line, he closed an electric circuit by means of a key, thus causing the electro-magnet to attract its armature and convey to the operator at the distant end of the line the conventional signal.

Naturally, the operation of the Morse telegraph suggested the possibility of transmitting the voice itself to a distance, and, indeed, as early as 1854 we find Charles Boursel publishing to the world the possibility of speech transmission in words that have since become historic. He said: “I have asked myself if the spoken word itself could not be transmitted by electricity; in a word, if what was spoken in Vienna may not be heard in Paris. . . . Suppose that a man speaks near a movable disk sufficiently flexible to lose none of the vibrations of the voice; that this disk alternately makes and breaks the connection with a battery; you may have, at a distance, another disk which will simultaneously execute the same vibrations.”

Boursel erroneously supposed that the voice could be transmitted by the opening and closing of the circuit, and thus outlined a path of research which science traveled for twenty years, until Bell, by his theory of electric undulations, removed it from the deeply-worn rut.

In 1861 Philip Reis, of Frankfort, Germany, apparently following the instruction of Boursel, constructed the first telephone, which comprised as a transmitter a diaphragm, adapted in its vibration to open and close an electric circuit. At the receiving station was placed an electro-magnet, which, by the successive current impulses, sent over the line by the transmitter, caused the magnet to alternately attract and release its armature, to which was secured a thin plate, which, in the vibration of the armature, was moved back and forth, thus beating the air and setting in motion the air particles that conveyed to the ear the sense of sound.

By comparing the telephone of Reis with the telegraph of Morse, it will be observed that the transmitting instruments differ only in that Morse used a key actuated by the hand for opening and closing the circuit, while Reis provided a diaphragm which, for the sake of the analogy,we may consider a key, adapted to be actuated, not by the hand, but by the vocal organs. Again, the only essential difference between the receiving instruments was that Reis had applied to the armature of the Morse instrument a thin plate for the purpose of setting the air particles in motion.

Reis, by opening and closing the circuit, was unable to transmit the complex current undulations upon which we know the transmission of articulate speech to depend, and was able to transmit only simple musical sounds. It has been contended by some that Reis actually transmitted articulate speech by means of his apparatus by causing the contacts to remain continuously in contact, so as to produce an undulatory instead of an intermittent current, and, in fact, with the assistance of our present knowledge, speech may be transmitted by apparatus constructed after that manner. But that Reis himself did not understand the necessity of an undulatory current and did not transmit speech, may be inferred from the fact that in his later apparatus, which was considered by him an improvement upon the former, the construction was such that it was impossible to cause the contacts to remain continuously in contact.

The apparatus of Reis, as Reis used it, was incapable of transmitting articulate speech, since the only effect of each vibration of the diaphragm was to close the circuit of a battery and send a current impulse over the line. These current impulses being always of the same strength, the vibrating plate of the receiver always produced tones of a given loudness, but as the rate of vibration of the transmitter varied, the rate of vibration of the receiver plate correspondingly varied, the apparatus being thus capable of reproducing the pitch of the sounds. But in complex sounds, and particularly sounds comprising articulate speech, the air particles do not perform a simple to-and-fro movement in constituting the sound, but perform the cycle with more or less complexity, now advancing rapidly, now slower, perhaps receding slightly, and then advancing to complete the stroke, and it is evident that any transmitter that fails to register all of these variations will fail to transmit articulate speech. Since the transmitting diaphragm of the Reis telephone merely registered the completion of the stroke and not the intermediate movements, it was, of course, incapable of transmitting articulate speech.

In the early seventies, Alexander Graham Bell was working upon a harmonic telegraph which, in its essential features, comprised a permanent magnet, opposite the pole of which were located a number of reeds, each adapted to vibrate at a different rate. Encircling the magnet was a coil of wire connected with the coil of a similar instrument at a distance. When one of the reeds was set in vibration, it executed a definite number of vibrations, the number being peculiar to the reed, and the successive approach of its end to the end of the magnet varied the strength of the magnet, thus inducing in the coil a current which, traversing the coil at the receiving station, varied the strength of the magnet which it encircled to cause the successive attraction of a reed having the same characteristic vibration. None of the reeds at the receiving station thus vibrate except those whose correspondents at the transmitter vibrate, and if a number of the reeds at the transmitting station are caused to vibrate, the corresponding reeds at the receiving station are set in vibration.

HISTORICAL TELEPHONE DIAGRAMS.

Now, since complex sounds may be resolved into a number of superimposed simple sounds, Bell concluded that if the reeds be mounted flexibly enough to vibrate under the influence of sound waves, and are sufficient in number, a person, in speaking against the reeds, would set such reeds, the vibration of which when compounded produce the sound, into vibration, thus causing the corresponding reeds at the receiver to vibrate and reproduce the sound. From this conception of the production of all the simple tones of which the complex tone is composed, Bell, taking a lesson from the human ear, advanced to the conception of a diaphragm which should not have a characteristic vibration to respond to a particular sound, but which should respond to all sounds, and the development of this idea led to the production of the magneto-telephone.

Bell perceived the mathematical requisite for the transmission of speech before he had conceived the means for embodying it in material form. Sir William Thomson, now Lord Kelvin, commenting upon this achievement of Bell, remarked: “We can but admire the hardihood of invention that conceived such very slight means to realize the mathematical conception, that, if electricity is to convey all the delicacies of quality which distinguish articulate speech, the strength of the current must vary continuously, as nearly as may be, in simple proportion to the velocity of a particle of air engaged in constituting the sound.”

On the day that Bell filed his application for a patent, Elisha Gray filed a caveat in which he showed means for varying the resistance of the circuit to produce the undulatory current. He provided upon the diaphragm a needle which dipped into a cup of acidulated water, and, as the diaphragm vibrated, the needle was caused to approach or recede from an opposed circuit terminal, varying the resistance of the circuit.

Bell, in his patent specification, had likewise suggested the employment of means for varying the resistance of the circuit in the production of the undulatory current, and his first successful transmission of speech was accomplished with an instrument embodying this principle. The development of transmitting instruments has been made along this line, while the magneto telephone has been universally employed as a receiving instrument. To Berliner is attributed the invention of a resistance varying telephone, comprising solid electrodes continuously in contact, the varying resistance being accomplished by varying the pressure of contact of the electrodes by the vibration of the diaphragm. Edison conceived the employment of carbon for electrodes, whileBlake suggested the mounting of the electrodes individually upon springs, in a manner to prevent the breaking of the circuit. The transmitter has been improved by Hunnings by using granular carbon between a stationary plate and the vibrating diaphragm, thus securing a greater variation of resistance for a given movement of the diaphragm. The Hunnings transmitter, with improvements for preventing the caking of the granular material, marks the highest stage of development of the telephone transmitter.

Thus we see that the development of the telephone has been a gradual one, and has followed a logical course. It furnishes, perhaps, one of the most striking examples of the fact that great inventions do not spontaneously emanate from one mind far in advance of the age, but that each one simply adds his mite to the accumulated knowledge until some one happily supplies that one step which, added to what has gone before, carries the undertaking to success. The discoveries of Oersted and Sturgeon are properly steps in the march of progress and enabled Bell to make that one step — the discovery of the theory of undulations — which brought the efforts to transmit speech to a successful issue and laid the foundation for the later steps that have spanned continents with the human voice.