The transformation of this rudimentary means of communication into the beautiful mechanism which we have today forms a splendid chapter in the history of American invention.Of all the details in Bell's apparatus the receiver is almost the only one that remains now what it was forty years ago.The story of the transmitter in itself would fill a volume.Edison's success in devising a transmitter which permitted talk in ordinary conversational tones--an invention that became the property of the Western Union Telegraph Company, which early embarked in the telephone business--at one time seemed likely to force the Bell Company out of business.But Emile Berliner and Francis Blake finally came to the rescue with an excellent instrument, and the suggestion of an English clergyman, the Reverend Henry Hummings, that carbon granules be used on the diaphragm, made possible the present perfect instrument.The magneto call bell--still used in certain backward districts--for many years gave fair results for calling purposes, but the automatic switch, which enables us to get central by merely picking up the receiver, has made possible our great urban service.It was several years before the telephone makers developed so essential a thing as a satisfactory wire.Silver, which gave excellent results, was obviously too costly, and copper, the other metal which had many desirable qualities, was too soft.Thomas B.Doolittle solved this problem by inventing a hard-drawn copper wire.A young man of twenty-two, John J.Carty, suggested a simple device for exorcising the hundreds of "mysterious noises" that had made the use of the telephone so agonizing.It was caused, Carty pointed out, by the circumstance that the telephone, like the telegraph, used a ground circuit for the return wire; the resultant scrapings and moanings and howlings were merely the multitudinous voices of mother earth herself.Mr.Carty began installing the metallic circuit in his lines that is, he used wire, instead of the ground, to complete the circuit.As a result of this improvement the telephone was immediately cleared of these annoying interruptions.Mr.Carty, who is now Chief Engineer of the American Telephone and Telegraph Company, and the man who has superintended all its extensions in recent years, is one of the three or four men who have done most to create the present system.Another is Charles E.Scribner, who, by his invention of that intricate device, the multiple switchboard, has converted the telephone exchange into a smoothly working, orderly place.
Scribner's multiple switchboard dates from about 1890.It was Mr.
Scribner also who replaced the individual system of dry cells with one common battery located at the central exchange, an improvement which saved the Company 4,000,000 dry cells a year.
Then Barrett discovered a method of twisting fifty pairs of wires--since grown to 2400 pairs-into a cable, wrapping them in paper and molding them in lead, and the wires were now taken from poles and placed in conduits underground.
But perhaps the most romantic figure in telephone history, next to Bell, is that of a humble Servian immigrant who came to this country as a boy and obtained his first employment as a rubber in a Turkish bath.Michael I.Pupin was graduated from Columbia, studied afterward in Germany, and became absorbed in the new subject of electromechanics.In particular he became interested in a telephone problem that had bothered the greatest experts for years.One thing that had prevented the great extension of the telephone, especially for long distance work, was the size of the wire.Long distance lines up to 1900 demanded wire about one-eighth of an inch thick--as thick as a fairsized lead pencil;and, for this reason, the New York-Chicago line, built in 1893, consumed 870,000 pounds of copper wire of this size.Naturally the enormous expense stood in the way of any extended development.The same thickness also interfered with cable extension.Only about a hundred wires could be squeezed into one cable, against the eighteen hundred now compressed in the same area.Because of these shortcomings, telephone progress, about 1900, was marking time, awaiting the arrival of a thin wire that would do the work of a thick one.The importance of the problem is shown by the fact that one-fourth of all the capital invested in the telephone has been spent in copper.Professor Pupin, who had been a member of the faculty of Columbia University since 1888, solved this problem in his quiet laboratory and, by doing so, won the greatest prize in modern telephone art.His researches resulted in the famous "Pupin coil" by the expedient now known as "loading." When the scientists attempt to explain this invention, they have to use all kinds of mathematical formulas and curves and, in fact, they usually get to quarreling among themselves over the points involved.What Professor Pupin has apparently done is to free the wire from those miscellaneous disturbances known as "induction." This Pupin invention involved another improvement unsuspected by the inventor, which shows us the telephone in all its mystery and beauty and even its sublimity.Soon after the Pupin coil was introduced, it was discovered that, by crossing the wires of two circuits at regular intervals, another unexplainable circuit was induced.Because this third circuit travels apparently without wires, in some manner which the scientists have not yet discovered, it is appropriately known as the phantom circuit.The practical result is that it is now possible to send three telephone messages and eight telegraph messages over two pairs of wires--all at the same time.Professor Pupin's invention has resulted in economies that amount to millions of dollars, and has made possible long distance lines to practically every part of the United States.
