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Morse of America conceived the idea of the first practical recording tele graph while returning from Europe on the packet-ship "Sully" in Oct. 1832. In the course of conversation on board ship Faraday's recent (1831) publication on magneto-electric induction—the cur rent being induced by passing a magnet through a helix of wire forming part of a closed circuit—was discussed, and the fact that a charge of electricity can thus be almost instantaneously passed along a length of wire was referred to by Dr. Watson of Boston. These two facts led Morse to the conclusion that if the presence of electricity could also be detected in any desired part of the circuit it should be possible to record signals instantaneously by opening and closing the circuit. Before his arrival in New York on Oct. 13, Morse had made his plans for a telegraph recording instrument, and laid the principles for his dot-dash-space code based on the duration or the absence of the electrical impulse over a circuit. Three years later Morse constructed an experimental model of his telegraph (fig. 3) which, by the mechanical action of an electromagnet A, operated a lever B carrying a pencil C at one extremity. The passage of electrical impulses through the electromagnetic circuit caused the pencil to move in contact with a paper tape D passing over a revolving cylinder E directly under the pencil, thus drawing an undulated line embodying his code. The speed of the paper was regulated by clockwork F. A single wire conductor connected one pole of the battery G to one end of the helix of the electromagnet ; the other end of the helix was connected to one of two cups of mercury on the "port rule," the second cup being connected to the second pole of the battery, so that the only part of the circuit not complete was between the two cups of mercury H. The electric impulses were imparted to the wire at the sending end by causing the metallic projections at the end of the lever .1 to dip into the two mercury cups, thus closing the circuit. The projections K arranged on the 3 ft. piece of wood L actuated the lever and were so spaced as to form his code. This crude model was privately exhibited at New York University in 1835, and enlisted the interest of Gale and Vail.
The latter subsequently furnished Morse with the means, material and labour for an experiment on a larger scale.
Morse Relay.—In 1836 Morse constructed duplicate apparatus so that the telegraph might be operated in either direction. As the experiments progressed it was found that the electric current, after passing over a wire 20 m. or so in length, became too feeble to operate the receiving apparatus directly. With the assistance of Gale and Henry, Morse devised a relay which would auto matically repeat signals into another section of line and join cir cuits in this manner for any desired distance. The application of these relays is shown in fig. 4. Suppose the sent current is re ceived in relay magnet A, energization of this magnet will cause its armature to be rotated against the retractile force of counter weight F, causing the wire C to dip into mercury cups N and 0, thus closing the circuit through battery I, relay magnet B, and the second section of line. The second relay actuated by magnet B will respond in a similar manner and repeat into a third section, etc., until the receiving apparatus is finally actuated.
Morse Key.—In the improved apparatus, for which Morse filed a caveat in the U.S. Patent Office on Oct. 6, 1837, a number of
modifications had been made by Vail. The port rule was aban doned in favour of a simple cir cuit closer or key, by which the signals could be formed by hand. For the original pencil-marking method could be substituted any , one of three recording methods: a fountain pen (fig. 5), an inked wheel (fig. 6) or a stylus which indented the paper (fig. 7).
The Sounder—In April 1844, however, Vail made the valuable discovery that it was possible to read messages by sound. He found that as a dot or dash is recorded the lever makes two dis tinct sounds, one as it strikes against the stop which limits its motion in one direction and again as it strikes in retreating against the stop which limits its motion in the other direction; when a dot or short line is recorded the interval is shorter than when a long line is recorded, and signals can thus be read by the length of the intervals between sounds. Following upon this discovery the Morse register or record ing instrument passed into dis use.
On April 7, 1838 Morse made formal application for a patent which was granted on Oct.
1848. On Feb. 21, 1838 he had demonstrated his telegraph before the U.S. president and his cabinet, and a bill was subsequently passed appropriating $30,000 to be expended on a series of experiments to test its practicability.
About a year after the passage of the bill an experimental line was completed between Washington and Baltimore, a distance of 40 miles. The line was opened for public business and its im mense value to the State became apparent ; but when Morse of fered the telegraph to the Gov ernment for $1oo,000 his offer was refused upon the recom mendation of the postmaster general, as he was "uncertain that the revenues could be made equal to its expenditures." Morse then enlisted private capital and in 1844 a company was organized to erect a telegraph line between New York, Baltimore and Washington. By 1851, 5o companies using Morse telegraph patents were in operation in the United States and by 1861 Morse patents were in operation in Europe.
Many telegraph circuits in various parts of the world still employ the fundamental principles of the original Morse system. Upon circuits of this class, which are operated by the single current method, signals in accordance with the Morse code are transmitted as short and long pulses of current separated by intervals of various lengths during which no current flows. The short and long pulses of current are termed respectively dots and dashes.
Code.—The dot is a very short signal ; when made by hand on a telegraph key the lever is depressed for about nth of a second. The dash lasts about
of a second. These periods of time correspond to 3o average words per minute on land lines. The dot is the unit by which the length of the dashes and spaces are measured. The dash is equal to the length of three dots. The space between components of a letter equals one dot, except in certain dot letters in American Morse which contain a space equal to two dots. The space between the letters of a word is dots and dashes traverse the circuit in one direction and the space pulses in the opposite direction. This is readily accomplished by connecting the negative pole of the transmitting battery to the line for each dot or dash, and the positive pole for each space.