TELEGRAPH, an apparatus or proc ess for the rapid communication of intel ligence between distant points, especially by means of electromagnetism. The in vention of the electric telegraph, as now used in all parts of the world, is due to Samuel F. B. Morse, who, in 1832, dur ing a homeward voyage from France to New York, conceived the idea of writing on a distant strip of moving paper by means of a pencil worked by an electro magnet and a single conducting circuit, and who in 1844 completed the first line between Washington and Baltimore, and transmitted the first message May 27 of that year. The invention of the Leyden jar, and the discovery of the fact that the earth and intervening bodies of water may be employed as part of an electric circuit, were among the most important steps which gradually led to the comple tion of the present system of telegraphy. There are now about 500,000 miles of line in operation in the world, using over 1,000,000 miles of wire.
The leading principle in the Morse and other allied instruments is that by the depression of a key or other method, an electric circuit is "closed" or completed, and a signal is transmitted along the wire to the distant station, where, on its arrival, it reproduces the signal by the action of an electro-magnet or otherwise. Electrically the Morse consists of a transmitting key and an electro-magnet and armature; while mechanically it con sists of a lever, with circular wheel or disk attached to the armature, and a clockwork arrangement, by which the pa per tape to be printed on is carried for ward under the disk. In the first Morse instruments the marks were made on the paper with a pointed style (the instru ment being thus known as the "embos ser"), but by the invention of the ink writer, a form of register now much used in Europe and Asia, the legibility and permanence of the record are secured, be sides the advantage that a very light cur rent will serve to make the marks.
The instrument most in use in the United States and Canada, as well as in India and to some extent in Europe, is the "sounder," which is simply a Morse register stripped of all its parts except the electro-magnet, the lever, and the spring, the operator reading by the click ing sounds caused by the opening and breaking of the circuit. By this method the message is read and copied simulta neously, the speed of transmission is greatly increased, and the experience has proven that the proportion of errors is much diminished. The American Morse alphabet, used in the United States and Canada, is as follows: The International Morse alphabet is used in all other parts of the world. The signals, as given below, are arranged in the groups, and accompanied by the mnemonic phrases adopted by the Brit ish Postoffice when, in 1870, the transfer of the telegraphs to the government ren dered necessary the rapid training of thousands of operators throughout the kingdom: Each figure is represented by five sig nals, but on busy circuits expert clerks adopt the practice of "sending short," omitting all after the first dash in the figures 1, 2, 3, and 4, and all before the last dash in 7, 8, 9, and 0. It is stated
that Professor Morse founded his alpha bet upon information given him by his brother, a journalist, as to the numerical relation of the letters in the English al phabet, the simplest signal (a dot) being given to E, and the next simplest (a dash) to T, those letters occurring most frequently in our language. The inter national alphabet is considered prefer able, as it contains no spaced letters, which sometimes gives rise to errors in reading.
The process of transmitting more than one communication at the same time over the same line, known as the "duplex" method, was first introduced in the United States, and afterward in Europe, by J. B. Stearns, of Massachusetts, who made his first successful experiment in 1852. The "quadruplex" method was invented by Thomas A. Edison in 1874. Subsequent improvements have been made, and the multiple pro cess, in one form and another, is now extensively used, by means of which the working capacity of the lines is in creased at least 25 per cent. An auto matic telegraph, in which the message was transmitted from a -strip of paper punched with holes representing the let ters, was invented in 1846 by Alexander Bain, of Scotland, and afterward im proved by Siemens, of Berlin; Humas ton, of Connecticut; and Wheatstone, of England. The autographic process, transmitting a facsimile of the original dispatch, was first brought out in 1848 by F. C. Bakewell, of London, and im proved by Abbe Casselli, of Florence; Lenoir and Meyer, of France; and Saw yer, of Washington, D. C. (see TELAUTO GRAPH) . The printing telegraph for re cording messages in Roman characters was first suggested by Alfred Vail, of New Jersey, in 1837. The first model of this telegraph was made by Wheatstone in 1841. Various modifications of this instrument by different inventors are now in use for transmitting private dis patches and for the reporting of com mercial and financial fluctuations. In 1918 there were 238,000 miles of pole lines in the United States, and 35,000 in Canada, not including the railroad com panies' special lines. There are over 435,000 miles of lines in other countries, and over 200,000 miles of submarine cables.
See SUBMARINE TELEGRAPHY: WIRE LESS TELEGRAPHY.