Inventions of the Great War

g in t

States held almost a monopoly and the pro

so as to cut out the terrific roar of his own engine. Now the range of his voice has been so extended that he can chat with fellow aviators miles away. This remarkable achievement and many others in the field of radio-communication hinge upon a delicate electrical device invented by Deforest in 1906 and known as the "

AU

ve to give a brief outline of its construction and operation for the benefi

he bulb and at the opposite side there is a metal plate. When the plate and the filament are connected with opposite poles of a battery, there is a flow of current between them, but because only negative electrons are emitted by the filament, the current will flow only in one

of the strength of the electric current between plate and filament. The slightest change in electric power in the grid will produce large changes of power in the current flowing through the audion. This makes it possible to magnify or ampli

NEW YORK TO

fresh relay of current. But these devices distorted the message so that it was unintelligible. The range of wire telephony was greatly increased by the use of certain coils invented by Pupin, which were placed in the line at intervals; but still there was a limit to which conv

sed the range of radio outfits. Messages could be received from great distances without any extensive or elaborate a?rials, an

ephone company began to experiment with wireless telephony. They believed that it might be possible to use radio

ing radiotelegraphy and radiotelephony for the benefit of th

NATION OF RA

finally would reach the opposite stake and cause the float there to bob up and down in exactly the same way as did the float moved by hand. In wireless telegraphy the two stakes are represented by antenn? or a?rials and the cork floats are electric charges which are sent oscillating up

for a dash, there will be a long series of oscillations in the antenna, and for the dot a short series, and these short and long trains of waves will spread out to the receiving-a?rial where they will reproduce the same series of oscillations. But only a

itch that it could not be heard. So it is customary to interrupt the oscillations, breaking them up into short trains of waves, and these successive trains produce a note of low enough pitch to be h

ay of making perfectly uniform carrier-waves, and then of loading on them waves of speech. Of course, the latter are not sound-waves, because they are not waves of air, but they are electro-magnetic waves corresponding exactly to the sound-waves of air and at the receiving-end they affect the telephone receiver in the same way that it is affected by the electr

WITHOU

tried of talking from the big Arlington station near Washington to Darien, on the Isthmus of Panama. This was a distance of twenty-one hundred miles, and speech was actually transmitted through space over that great distance. That having pro

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d-gear of

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tion by Radio with a

ds for the use of radiotelegraphy, the French showed such an appreciation of science that they were willing to lend their aid to these experiments. The Eiffel Tower could be used only for short periods of time, and there was much interference from other high-powered stations. Nevertheless, the experiment proved perfectly successful, and conversation was carrie

Of course all vessels are equipped with wireless-telegraph apparatus, but there is a decided advantage in having the captain of one ship talk directly with the captain of another ship, or take his orders from headquarters, with an ordinary telephone receiver and transmitter. A special equipment was designed for battle-ships

stitute of Elec

Arlington (Va.) Station, with enlarge

came a call for radiotelephone apparatus for submarine-chasers, and

PHONES FO

most absurd to think that a delicate radiotelegraph apparatus could be made to work in the terrific noise and jarring of an airplane. The first task was to make the apparatus noise-proof. A special sound-proof room was constructed in which a noise was produced exactly imi

an?uvers, and it was also found that the helmet which was so satisfactory in the laboratory was not just the thing for actual service in an airplane. It had to fit very tightly around the ears and the mouth, and as the airplane went to high altitudes where the air-pressure was much lower than at the ground level, painful pressures were produced in the ears which were most annoying. A

he rush of air as it is carried along by the plane. But the speed of the airplane varies considerably. At times, it may be traveling at only forty miles per hour, and at other times as high as one hundred and sixty miles per hour, so that the little generator is subjected to great variations of speed and consequent variation

There was no way of getting rid of the magneto, but the wires leading from it to the engine were incased in metal tubes which were grounded at frequent intervals, and i

plane to the tail of the machine, and later it was found that by using two short trailing antenn? one from each tip of the win

orty-five miles. The conditions under which these distances were attained were unusual, and a distance of three miles was accepted as a standard for communication between airplanes. The apparatus weighed only fifty-eight pounds and it was connected with both the pilot and the observer so that they could carry on conversations wit

chasers were equipped with it, as well as a great many of our airplanes and seaplanes, and we furnished radio-apparatus sets to our allies which proved of immense value in the war. This was particularl

least, no elaborate a?rial will be needed, and with a small loop of wire, an audion o

WELVE HUNDRED

ne something like a type-writer, which, however, does not make type impressions, but cuts perforations in a long sheet of paper. The paper is then run through a transmitter at a high speed and the message is sent out at a rate of as much as twelve hundred words a minute. At the receiving-station, the message is received photographically on a strip of paper. The receiving-instrument has a fine quartz thread i

NG RADI

matter to rig up a wireless-telegraph system that will send messages to a considerable distance, and simpler still to rig up a receiving-set. European governments have always discouraged amateur radiotelegraphy, but in this country restrictions used to be so slight that almost an

e was plenty of it to be had everywhere. They could send orders to fellow workers and receive messages from them, or they could listen to dispatches sent out by the government and glean information of great military and naval importance. The

RELESS

and south. Now when a signal was received by the a?rial, if it struck the frame edgewise the radio waves would reach one side before they would the other. Taking a single wave, as shown by the drawing, Fig. 11, we see that while the crest of the wave is sweeping over one side of the frame, the trough of the wave is passing the other side. Two currents are set up in the radio compass, one in the wires at the near side of the compass, and another in the wires at the far side of the compass. As these currents are of the same direction, they oppose each other and tend to kill each other off, but one of the currents is stronger than the other because the crest of the wave is sweeping

the "Scienti

turned parallel to an onc

ass dial shows from what direction the signals are coming. At the same time, another line on the signals will be found by a seco

sible to locate the direction

dio compass. The truck would patrol the region located by the fixed compasses, and with it the position of the concealed station co

r the receiving of messages from distant points without a conspicuous a?rial an audion would have to be used and

SHIPS I

ompass could be used to find those who tried to hide, why co

soon will be, established at other ports. As soon as a ship arrives within fifty or a hundred miles of port she is required to call for her bearings. The operator of the control station instructs the ship to send her call letters for thirty seconds, and at the same time notifie

the "Scienti

tion of three radio compass stations and how positi

dial marked off in the 360 degrees of the circle. A thread passes through the chart and the hole in the glass at each station. These threads are attached to weights under the chart. When a compass station rep

it will also serve to prevent collisions at sea, because a ship equipped with

readful war, we have an apparatus that will