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The Telephone 167 But as the air-waves are translated at the trans- mitter into electrical waves to fly along the wire they must not interfere with one another as they travel. In other words, they must not tumble over one another, so to speak, or get in one another’s way. Although some 50,000 or more such waves are sent out during a single minute, each wave has a distinctive shape. They are just as different from one another as the waves of the sea. These differ- ences in form, as well as the distances between them, must be faithfully preserved and conserved during the journey over the wire, because, if not, they will be indistinguishable at the opposite end of the line. It is not a question of sending out one simple cur- rent, but perhaps as many as 120,000 different and tiny currents during the minute. Reaching the receiver each of these electrical waves has to be re- converted into its relative sound wave, which agi- tates the air sufficiently as to affect the ear and thereby enable the words to be distinguished. Another point has to be borne in mind. The problem of articulate speech transmission is not affected by increasing the loudness of the tones. You may yell into the telephone, but the sound at the opposite end is no louder than if you talked quietly and distinctly into the transmitter. The effort, producing the electrical waves which speed along the wire, is the weakest energy it is probably possible to imagine, being merely the amount of power set up by the human voice. These breaths start up the electrical waves, shape them, and time the distance between them, with the result that if the trans- mitter, line, and receiver are capable of fulfilling