Radio for Everybody, Austin C. Lescarboura, 1922, pages 48-50:
WHEN A RIVAL BECAME A PARTNER
And skipping over the numerous attempts to make something out of this remarkable laboratory toy, the wireless telephone, we come to the time when the American Telephone and Telegraph Company took an interest in the vacuum tube perfected by Lee de Forest, as is explained elsewhere in this work. In the vacuum tube the telephone engineers realized that they had found a solution to many of their problems. The vacuum tube is nothing short of an electrical acrobat; it can do all sorts of tricks which no other electrical device has ever been able to perform. Thus it is a wonderful alternating current generator; feed it direct current and it gives forth alternating current of a wide range of frequencies. It is this characteristic which makes it available for wireless transmission purposes. Feed it alternating current, and it delivers direct current. This characteristic, just the reverse from the preceding one, makes it available as a rectifier for charging storage batteries, and, some day in the near future, as a substitute for the elaborate and costly rotary converter units now necessary in electrical transmission work, for converting alternating current used in high-voltage transmission, back into direct current of suitable voltage for commercial use. Feed it high-frequency alternating current, such as radio waves, and it converts them into audible pulsating currents which affect telephone receivers and thus are converted into audible sounds. That is how it is used as a detector. Feed it ever so slight a fluctuating current, and it will control or modulate or modify a far more powerful current; thus we have the weak current moulding a powerful current, and it is this feature which gives us the amplifier. It is this characteristic, too, that makes the vacuum tube the finest telephonic relay ever devised. It is used in long-distance telephone communication, so that the voice currents, when greatly attenuated after traveling over hundreds of miles of wire, are brought to the grid member of the vacuum tube, and there serve to control a fresh and far more powerful current which starts off on the next lap of the journey, only to reach another vacuum tube when it in turn has become weak as a result of a long stretch. Again, the vacuum tube, because of its modulating characteristic, is the link between the carbon microphone or telephone transmitter of the ordinary kind, and the powerful currents of the radio transmitter. At a stroke it eliminates all the troubles that seemed impossible of solution back in the early days of the wireless telephone.
It was in 1915 that definite progress was first recorded in the history of the wireless telephone, for it was during the latter part of that year that the engineers of the American Telephone and Telegraph Company succeeded in telephoning by wireless between Arlington, Va., and the Eiffel Tower, in Paris, or over a distance of three thousand miles. Over three hundred vacuum tubes were employed to generate and modulate the high frequency current employed to span the Atlantic expanse. During the same tests the voice was carried through space all the way to Pearl Harbor, in the Hawaiian Islands, or a distance of almost five thousand miles.
Do not forget that the stock promoters, back in the days when wireless telephony seemed so impossible to the really wise men, were telling us that the wireless telephone would be the great rival of the wire telephone. The wire telephone would certainly be put out of business in due course. Yet it was only when the engineers of the wire telephone came to take an interest in wireless telephony that this art made real progress. What is more, they developed wireless telephony to something practical; and the wireless telephone, in turn, gave wire telephony the vacuum tube and other valuable devices which made long-distance telephony practical. So instead of proving rivals, these two great means of communication have come to be partners, and always will remain partners.