Radio Broadcast (May-Oct 1922)

2IO Radio Broadcast used selenium in an electric circuit with a telephone receiver, and, also vegetable fibre or lampblack placed in a glass bulb from which rubber tubes led to earpieces. On these substances (later it was demonstrated that many others could be used, such as a bit of black worsted cloth, of silk, or particles of rubber) the action of the rapidly varying degree of heat in the light rays caused the substances in the bulb to expel and absorb gases, alternately. These gases in turn produced vibrations in the air in the tubes and these vibrations made themselves felt in the eardums of the person listening, causing an exact reproduction of the words spoken at the transmitter. The instrument worked, and stood the test of many demonstrations. In the laboratories of the Bell Telephone Companies and later in those of the American Telephone & Telegraph Company, it was developed. There arc lights came to be used along with many other variations in Mr. Bell's original device. Thus in April, 1897, Hammond B. Hayes, one of the engineers of the American Telephone & Telegraph Company, noticed that a humming sound, audible in the receiver of the " radiophone," corresponded in pitch with that produced by the generator supplying the current for the arc lamp used in the experiments. Starting with this discovery Mr. Hayes concluded that if the words spoken into a telephone were made to act directly upon the lighting circuit, it would not be necessary to use the mirror employed by Mr. Bell and the distance which speech could be transmitted would be greatly increased. In other words, the telephone current could be superimposed upon the lighting current. This was done by attaching the telephone wires to the wires in the arc light. The principles remained the same, but with the improved device, which was patented in June, 1897, the sound of the voice could be heard with distinctness at points several miles from the transmitter, and it was known that good results might have been had at much greater distance. The instrument, as it now stands, is simple in appearance. The receiver used consists of a selenium cell enclosed in a glass bulb no bigger than that in which the homeopathic physician carries his pills. In making the cell, very fine brass wires are wound upon a bit of Indian pipe stone. The wires are then covered with a thin layer of selenium and are attached to the wires which connect with the telephone receiver. The glass bulb is then placed in a reflector which concentrates the rays of the lamp upon the selenium. At the sending end a searchlight such as is used on vessels is used. From the telephone transmitter, which is of special construction, wires lead to the lamp, and are attached to the wires which carry the lighting current. When words are spoken into the transmitter, the rays of the searchlight fluctuate. Standing by the lamp, however, an observer sees no change, of course. At the receiving end, which may be miles beyond visual distance by the naked eye, the selenium responds to these fluctuations in the light rays and the current in the wires there increases and diminishes in thousands of infinitesimal changes which reproduce not only the spoken words but the very tones of the voice of the speaker. The possibilities of the instrument, even though no results of its use with modern regenerators are available, are greater than may be supposed. Thus it had been found that an electric arc lamp is of itself a telephone receiver. The big light that hangs from a pole on the street corner may be made to talk! From the carbons in a lighted arc lamp there arises a column of vapor. If the lighting current is varied by superimposing upon it a telephone current, the column of vapor around the carbons in the lamp will fluctuate and sound waves corresponding to the words spoken into the telephone will be given out. Music can also be sent through the arc lamp — the notes of a bugle coming clear and distinct from an ordinary electric light when no bugler is in sight afford a striking illustration of things alread>done. The application of the instrument to maritime use has also been developed, and it would be possible for one ship captain in his cabin to hear another in his cabin, or to hear from the shoreline, by means of this, the original radiophone. it can be used in the da\time as well as in the night time, but fog is its enemy. It has been used by the German Government for lighthouse work, and by the U. S. Signal Corps. It may yet be that the "talking arc," will come into its own, in spite of, or even in