HISTORY OF THE WIRE COMMUNICATIONS: BEGINNINGS OF THE TELEGRAPH AND THE TELEPHONE.

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The wireless telegraph .

When James Clerk Maxwell (1831-1879) , one of the greatest English mathematical scientists, suggested, in 1864, that the light that we receive from the Sun was transmitted through the intermediate space and at a distance of 148,800,000, kilometers by means of fast ether vibrations, he also predicted the probable existence of other slower ether vibrations than did not produce any effect on our sight. Since then many men of science tried to prove the existence of these vibrations. The first convincing test of its presence was presented by Dr Heinrich Hertz (1857-1894), a young German professor. The glory of the discovery of the transmission of energy through the ether must, therefore, be distributed between Maxwell, that predicted it, and Hertz, that discovered it and showed its vibrations.

Hertz generated the electrical vibrations discharging a condenser at a short distance of the ends of it by two conductors connected with the terminals of the condenser.

The vibrations of the ether were discovered placing at some distance of the condenser a simple coiled wire interrupted in a small distance and watching that a spark jumped from this gap. He so demonstrated that an electrical spark that jumps in a point produces an electrical current in a wire placed in another place. He attributed this distant effect of the spark to the vibrations of the ether that carried some kind of vibration of the condenser that discharged until the circuit formed by the coiled wire . Hertz also demonstrated that these ether vibrations could be reflected in the same way that the light is reflected in a mirror; but they differed from the luminous vibrations in which those ones could pass through substances that the light was not able to cross.

BRANLY'S COHERER ELECTRICAL DIAGRAM

Sir Oliver Lodge, then professor of the The University of Liverpool and the professor Augustus Righi, of the University of Bologna, granted considerable attention to the discovery of Hertz and made many investigations on the properties of the vibrations of the ether. In 1889, professor Edouard Eugène Désiré Branly (1844 - 1940), French physicist, professor of The Catholic University of Paris, made the important discovery that a tube containing small metal filings placed in a crystal tube became more compact under the influence of the ether vibrations. With the Branly's coherer it was then possible, by means of the disposition shown in the attached figure, to ring a bell placed remotely of a condenser that produced a spark by discharge as it has been indicated previously. When the terminals of the loaded condenser were close enough so that the spark jumped , the vibrations of the ether caused that the metallic filings that were loose in the coherer tighten and form a mass compact enough to establish the connection between the battery and the bell.

Guglielmo Marconi

The experiments of Hertz, Lodge and Righi were oriented towards a more complete knowledge of the properties of the vibrations of the ether, and none of these wise people tried at first to develop any procedure of transmission of signals. The work of Hertz was interrupted abruptly by his premature death in 1894 .

Guglielmo Marconi, an Italian young person, who was interested in the investigations of Righi and the other wise people, began to experiment in 1895 by himself on the effects that the electrical sparks produced in remote coherers. Marconi discovered in a moment that the vibrations of the ether influenced the coherer at a greater distance if one of the poles of the spark and the coherer were each connected to earth and the other poles of each one were connected with a vertical wire. Connecting one of the windings of an induction coil to two metallic spheres (as it had already been done previously), Lodge could make work a remote telegraphic receiver about 100 meters away , closing the circuit of the battery of the induction coil, as it is shown in the attached picture. Marconi also maintained the filings of the coherer in a state ready to work, blowing it electrically, what caused that after the filings had gathered, forming a compact mass, they were again separated and they responded thus to the following signal again.

At this time other many wise people became interested in the development of the wireless telegraphy . Experiments were made in England by sir Oliver Lodge, Dr Muirhead and the captain Jackson, in Russia Count Popoff, in Germany by the professor Slaby, in France the professor Branly, and in the United States by Nikola Tesla, the professor Fessenden and De Forest. Marconi , nevertheless , made greater advances than the others, and in 1896 he obtained in England his first patent of the telegraph without wires .

Under the protection of the British government an extensive series of experiments began, in which the transmission range was gradually increasing from about 100 meters to several kilometers. In 1899 it was contacted by wireless telegraph through the English Channel, at a distance of about 60 kilometers. In all these experiments the equipment used was in essence the same that he had firstly constructed. He reached greater distances producing stronger sparks and raising higher antennas.