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In September last appeared in this Journal an article entitled ' Singing and Talking by Telegraph ;' and in that paper we attempted to describe the mechanism of that wonderful little instrument the telephone. It is now our purpose to say something regarding the progress that has been made towards perfecting the invention ; but in order to make the article as clear as possible, we venture once more upon a few words explanatory of the instrument.

The telephone as it is now made is an exceedingly simple-looking apparatus similar in appearance to a stethoscope ; to the handle of a girl's skipping-rope; or better still, to a large-sized penny wooden trumpet. Inside this hollow cylinder, and within an inch or so of the wider end, is fixed a plate of iron as thin as a well-worn sixpence, and about the size of a half-crown piece. This is called the diaphragm. Behind the diaphragm, nearly touching it, and extending to the narrower end of the cylinder, is a piece of ' soft' iron enveloped in wire coils, with a permanent magnet beyond. Outside the narrower end of the cylinder, and communicating with the coils that surround the iron inside, are attached two screws or 'terminals,' which are 'joined up' to a main wire, communicating with the distant or receiving telephone wherever that may be, and which is precisely similar to the one we have described. When we apply our mouth to the bell-shaped end of the apparatus, and speak or shout or sing, we set the diaphragm vibrating as in a tuning-fork ; the vibrations thus created are electrically communicated through the wire to a distant telephone, and are repeated on its diaphragm with more or less distinctness.

It is known that the motion of an iron plate contiguous to the poles of a magnet creates a disturbance of electricity in coils surrounding those poles; and the duration of this current will coincide with the vibratory motion of the plate or diaphragm. When, therefore, the human voice (or any other suitable sound) impinges through the tube against this diaphragm, the diaphragm begins to vibrate, and awakens, so to speak, electrical action in the coils of wire surrounding the poles of the magnet ; not a current, but a series of undulations, something like those produced by the voice in the air around us. In short the telephone is an apparatus designed to transmit sound through a wire o£ indefinite length ; the voice being, so to speak, 'converted into electricity at one end, the electricity becoming voice at the other.'

With these few explanatory remarks, we now proceed to offer to our readers the following interesting experiments made by a gentleman well skilled in telegraphy.

'Journalists,' he says, 'with no special knowledge of the difficulties the invention has to encounter as a telegraph instrument, have expatiated in such enthusiastic terms upon the results said to have been achieved by the telephone, that a somewhat exaggerated notion of its powers and capabilities has been accepted by the general public. It appears, therefore, to the writer of those lines that a statement of the experiences of a person practically engaged in the work of telegraphy may assist in placing the phenomena of the telephone on a proper footing.

'Scientifically, the telephone is a great and undoubted success ; and a person would be grievously in error if, because of some undoubted hindrances to its practical use, he pronounced it unworthy of further experiment. The emergence of telegraphy from the domain of experiment into that of daily practical use is a fact so undoubted, and one with which we are now so familiar, that it is impossible to say at what moment the telephone, at present a scientific toy, may become a daily necessity not only of telegraphic but of ordinary commercial work.

'Being engaged in daily contact with a large telegraphic centre, and in association with men who have the command of every means of testing the invention in a practical work-a-day manner, the writer was able to gauge pretty accurately the range within which the telephone can work. It must be understood, however, that in recording the effects observed by him and his associates, he has no desire to invalidate, or even to call in question the experiences of others who may have been able to arrive at better results. The telephone is in the hands of some of the first electricians and telegraphists of the day, and differences of conditions (not to speak of differences of capacity on the part of the operator) may give variety in the observations made. The very difficulties and drawbacks now to be recorded will no doubt some day suggest to a master-mind the method by which they may be overcome. But till that day arrives, the telephone must be content to remain where the writer leaves it, an undoubted success from a scientific point of view, but overwhelmed with obstacles to its practical use, in this country at least, in general telegraphy’.

'When a telegraphist first gets into his hand this beautifully simple and electrically delicate instrument, his first inclination is to test its carrying-power. This is of course a closet experiment, not working with actual telegraph line, but with "resistance" equivalent to a telegraph line of stated length. An experiment of this nature gives better results than could be obtained by a veritable line, because the insulation is, so to speak, perfect. No leakage at undesigned points of contact, or disturbance from unfavourable atmospheric conditions, is felt, and the experiment is entirely under the observer's control. The apparatus used is designed to offer the same labour for the electric current to overcome, as would be offered by a stated length of outside telegraph line. This artificial resistance is nicely graduated, and as the method of testing was suggested by Ohm, a German electrician, the unit of resistance is, as we once previously explained, termed an "ohm." Removing the telephone to such a distance that the two observers were "out of earshot," the test with resistance was tried, and with a resistance of one thousand ohms—roughly speaking, equal to seventy miles of a well-constructed line—the sound was perfect, although not very loud. Every articulation of the speaker at the other end could be distinguished so long as silence was maintained in the room, or so long as no heavy lorry rumbling over the stones outside sent in harsh noises which drowned the faint whisper of the instrument. The resistance was gradually raised to four thousand ohms—nearly three hundred miles—with like favourable results ; and for some little distance beyond, articulation could still be made out. But by the time ten thousand ohms had been applied, putting the speaker at a distance of, say, seven hundred miles, sound only, but not articulate sound, reached the ear. The tone was there, and every inflection of the voice could be followed; but articulation was absent, although the listener strove every nerve to catch the sound, which the speaker, as was afterwards ascertained, was shouting in a loud clear voice. The prolonged notes of an air sung could be heard with the resistance named, but again no words could be distinguished. The voice, whether in speaking or singing, has a weird curious sound in the telephone. It is in a measure ventriloqual in character; and with the telephone held an inch or two from the ear, it has the effect as if some one were singing far off in the building, or the sound were coming up from a vaulted cellar or through a massive stone wall.

'Proceeding to our next experiment, we joined up the telephones in one office to several wires in succession, putting ourselves in circuit with lines going to various distances and working with different instruments. When this was done, the real obstacle to telephonic progress at once asserted itself in the shape of "induction." The first wire experimented with was partly "overhouse" and partly underground, and the offices upon it were working Wheatstone ABC instruments. It is difficult to render clear to the person ignorant of telegraphic phenomena the idea expressed by the word induction. Briefly it may be put thus, that when a strong electric current is passing on a wire, it has the faculty of setting up a current of opposite character in any wire not then working or working with a feebler current, that may be in its vicinity. The why or the wherefore cannot be explained, but there is the fact.

'In various recent articles on the telephone mention has been made of "contact" as the cause of disturbance. This word, however, although it has been used by telegraphists, is misleading, and can only be used as an endeavour to express popularly an electric fact. Actual contact of one wire with another would spoil the business altogether. A wire bearing an electric current seems to be for the time surrounded, to an undefined distance, by an electric atmosphere, and all wires coming within this atmosphere have a current in an opposite direction set up in them. This is as near an explanation of the phenomena of induction as the state of telegraph science at present affords. Now the telephone works with a very delicate magnetic current, and is easily overpowered by the action of a stronger current in any wire near which the telephone wire may come. To work properly it "requires a silent line."

'In the place where the observations were made, there are a large number of wires, travelling under the floor, through the test-box, along passages to the battery-room and to a pole on the outside, whence they radiate, or out to a pipe underground, where many gutta-percha-covered wires lie side by side. On applying the ear to a telephone joined into a circuit working in such an office a curious sound is heard, comparable most nearly to the sound of a pot boiling. But the practised ear could soon separate the boiling into distinct sounds. There was one masterful Morse instrument—probably on the wire lying nearest the one on which we were joined up—whose peremptory "click, cli-i-i-ck, click," representing "dot, dash, dot" on the printed slip we read from, could be heard over all. Then there was the rapid whir of a Wheatstone fast-speed transmitter, sending dots and dashes at express speed by mechanical means ; the sharp well-pronounced rattle in sounds of equal length of a needle instrument ; and most curious of all, the "rrrrr-op, rr-op, rrrrrrrrrrrrr-op, rrrrr-op, rr-op" of the ABC, the deadliest foe to the telephone in its endeavours to gain admission into the family of telegraph instruments. There may be reason in this, for as the Wheatstone ABC is the instrument used for private telegraphy, or for the least important public offices, because it requires no "code" to be learned by the manipulator, so it would likely be the first to be displaced if an acoustic telegraph permanently took the field. So the sentient little ABC opens its mitrailleuse fire on the intruder, on whose delicate currents, in the words of an accomplished electrician, it plays "old harry." The peculiar character of the sounds we borrow on the telephone from this instrument arises from the fact that as the needle flies round the dial, a distinct current or pulsation passes for each letter, and the final "op" we have tried to represent shews the stoppage of the needle at the letters as words were spelled out.

'It must not be understood that the sounds of those various instruments are actually heard in the telephone. What happens is, that the currents stealing along the telephone wire by induction produce vibrations in the diaphragm of that instrument, the little metal membrane working on the magnet in ready response to every current set up in the latter. When it is remembered that the principle of the telephone is that the sound-caused vibrations in the filmy diaphragm at one end create similar but magnetically-caused vibrations in the diaphragm at the other end, and so reproduce the sound, it will be obvious why the rapid roll of the ABC currents, or the swift sending of the fast-speed transmitter, when brought by induction into the telephone wire, cause disturbances in the sound vibrations, and thereby cripple the instrument. One instrument of either kind named would have a certain effect, but one Morse or single needle would not have any greatly prejudicial effect. But a number of Morses or needles going together, such as were heard in our experiments, would combine to be nearly as bad as one ABC or fast-speed Morse. So delicate is the diaphragm to sound (and necessarily so), that in all experiments with the telephone itself, such as those with "resistance," or those made at home to test the instrument apart from telegraphic considerations, every sound from without broke in, giving an effect like the well-known "murmur of the shell."

'Joining up our wire now to a more distant station at some miles along the railway, and having on its poles a number of what are known as "heavy" circuits, the pot-boiling sound assumed even more marked characteristics. The ABC no longer affected us; but a number of Morse instruments were in full gear, and the fast-speed transmitter was also at work. While we were listening, the circuit to which we were joined began to work, and the effect was literally electrical. Hitherto we had only borrowed currents —or, seeing they were so unwelcome, we might call them currents thrust upon us—and the sounds, though sharp and incessant, were gentle and rather low. But when the strong current was set up in the wire itself, the listener who held one of our telephones nearly jumped from the floor when an angry "pit-pat, pit-pat, pit-pat-pit" assailed his ear, causing him to drop the instrument as if he had been shot! It was a result none of us had expected, for it did not seem possible that the delicate metal diaphragm and the little magnet of the telephone could produce a sound so intense. Of course it was only intense when the ear was held close to the orifice of the instrument. Held in the hand away from the ear, the telephone now made a first-rate "sounder," and we could tell without difficulty not only the signals that were passing, but found in it a more comfortable tone than that given by the Morse sounder in common use.

'Other experiments of a like character led to results so similar, that they may be left unnoticed ; and we proceed now to describe one of a different character, designed to test the telephone itself. At a distance of about half a mile, access was obtained to a Morse instrument in private use, and joined to the office by "overhouse" wire. Dividing our party and arranging a programme of operations, two remained with a telephone in the office, while other two, of whom the writer was one, proceeded with the second telephone to the distant instrument. By an arrangement which a practical telegraphist will understand, the key of the Morse was kept in circuit, so that signals could be exchanged in that way. It may be noticed, however, that this was hardly necessary, as the diaphragm, of the telephone can be used as a key, with the finger or a blunt point, so that dot and dash signals are interchangeable, should the voice fail to be heard. As the wire in this instance travelled almost alone over part of its course, we were in hopes that induced currents would be conspicuous by their absence. In this we were, however, disappointed, for the pot was boiling away, rather more faintly, but with the "plop-plop-plop" distinctly audible, and once more a sharp masterful Morse click was heard coming in now and again. The deadly ABC was, however, absent, so that our experiment proved highly successful. For some reason or another—probably an imperfect condition of the wire, or the effects of "induction" over and above what made itself audible to us—the spoken sounds were deficient in distinctness ; but songs sung at either end were very beautifully heard, and indeed the sustained note of sung words had always a better carrying-power than rapidly spoken words. Every syllable, and every turn of melody of such a song as My Mother bids me bind my Hair, sung by a lady at one end, or When the Heart of a Man, sung at the other, could be distinctly heard, but with the effect before noticed, that the voice was muffled or shut in, as if the singer were in a cellar, while it was not always possible to say at once whether the voice was that of a man or a woman.

'In the course of some domestic experiments, it was remarked that in playing the scale downwards from C in alt. on the piano, the result to the listener was a "tit" only for the four upper notes, although all below that had a clear "ting," and the octaves below were mostly distinct, although at the low notes of the piano the sound was again lost. The ringing notes of a musical box were not so successful, but with close attention, its rapid execution of Tommy Dodd could be well enough made out. An endeavour was made to catch the ticking of a watch, but this was not successful, and the experiment is not recommended, as the near presence of a watch to a magnet is not desirable ; and the watch exposed to it in this instance was, it is thought, affected for a short time thereafter, although it received no permanent damage.

'The observations made in the course of these experiments convinced those present that the telephone presents facilities for the dangerous practice of "tapping the wires," which may make it useful or dangerous, according as it is used for proper or improper purposes. It might be an important addition for a military commander to make to his flying cavalry ; as an expert sound-reader, accompanying a column sent to cut off the enemy's telegraph connections, might precede the act of destruction by robbing him of some of his secrets. The rapidity and simplicity of the means by which a wire could be "milked," without being cut or put out of circuit, struck the whole of the party engaged in the various trials that are described above. Of course the process of tapping by telephone could not be carried out if the instrument in use was an ABC or single needle, or if the wire was being worked duplex or with a fast-speed Morse, for in these cases the sounds are too rapid or too indefinite to be read by ear. The danger is thus limited to ordinary sounder or Morse telegraphs; but these still form the mainstay of every public system.

'Since the trials above described were made, the newspapers have recorded a beautiful application by Sir William Thomson, of the electric part of the telephone to exhibit at a distance the motions of an anemometer; the object being to shew the force of air-currents in coal-mines. This is a useful application of an electric fact, and doubtless points the way to further discoveries. But it is to be noticed that the experiment, interesting as it is, hardly comes under the head of a telephone, what is reproduced at a distance being not sound but motion.

'Obviously the invention cannot rest where it is; and no one more readily than the practical telegraphist will welcome an instrument at once simple, direct, and reliable. Even in its present form the telephone may be successfully used where its wire is absolutely isolated from all other telegraph wires. But the general impression is that its power of reproducing the sound must be intensified before its use can become general even as a substitute in works or offices for the speaking-tube.'

Published on December 22nd 1877 in Chambers’s Journal of Popular Literature, Science and Art.

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Privateline.com: Telephone History