Collier's New Encyclopedia (1921)/Wireless Telegraphy and Telephony

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Collier's New Encyclopedia
Wireless Telegraphy and Telephony

WIRELESS TELEGRAPHY AND TELEPHONY. A system of wireless telegraphy has been developed through three different methods, which may be classified as conduction, induction, and wave methods. By the method of conduction, currents are sent through the earth from one electrode to another, at the sending station. By the induction method, use is made of a property passed by alternating currents, of exciting similar currents in neighboring conductors with the aim of obtaining as intense a current as possible in the secondary circuit. The two methods were combined by W. H. Preece, of England. The third method is by the use of electromagnetic waves. This was introduced and developed by William Marconi, to whom is generally ascribed the invention of wireless telegraphy. After experiments were carried on through many years, practical use of wireless telegraphy was first demonstrated in the rescue of the steamship “Republic”, in 1909, and of the survivors of the steamship “Titanic”, in 1912. Both of these vessels were equipped with wireless telegraphy by which notification of disasters was given. Within a short period, all trans-Atlantic steamers and naval vessels were fitted with wireless telegraph apparatus, and wireless stations were erected in many parts of the United States, the British Isles, continental Europe, and other parts of the world. Service between the Eiffel Tower, Paris, and the United States was put into effect in 1911, and in 1913 wireless communication was established between Sayville, L. I., and Nauen, Germany. Direct communication by wireless telegraphy was established between the United States and Japan in 1915. During the World War practically all war vessels, including submarines, were equipped with wireless apparatus. Aeroplanes were likewise equipped with wireless installations and these proved an effective means of locating enemy troops and batteries. Wireless telegraphy was developed to a high state of efficiency during the war. It is also used for commercial purposes and in the transmission of news and commercial matter. The United States has established a widespread system of aerial communication. Stations are established at Arlington, Va., Panama Canal Zone, San Francisco, Pearl Harbor, Hawaii, in Samoa, and in the Philippine Islands.

Wireless Telephony.—A system of telephone communication in which the action of the transmitter brings about fluctuations in electric waves which are radiated through space by a high frequency current. These fluctuations are reproduced at the distant station in the form of the original sounds. Wireless telephony differs from wireless telegraphy in that the transmission of waves is continuous instead of interrupted. Wireless telephony has become a practical method of communication between ships at sea and between moving railroad trains. The distance to which sounds can be transmitted is practically limitless. Communication is held between New York and San Francisco, and between Arlington, Va., and Honolulu. The system was developed to a point of great efficiency in aeroplanes during the war. This use was especially notable in the great Meuse-Argonne campaign of 1918, when the American Signal Corps successfully directed operations beyond the lines by the use of wireless telephony.