The telegraph : Morse Code , circuits , aplications . Submarine telegraph .Photos .

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

The later use of the electromagnet as " a resonator " (it allowed to emit sound) came as an unexpected way. The operators got to be experts in receiving the telegraph dispatches to the ear, because the first printing method was left aside . The dot and dashes alphabet , invented by Morse, when used commercially in the United States, was seen that it was rather confused, by the fact that certain letters were only different by the intervals between the points, and it was frequently difficult to distinguish them between each other. The continental alphabet was free of this defect, and it was used in Europe generally in the submarine telegraph cable and in radiotelegraphy. It can seen as an example in the attached table the telegraphic codification of the maritime distress call asking for assistance sent by the ships in danger in the high seas or S.O.S. as three dots , followed by three dashes and three dots.

After demonstrating that the Morse telegraph could work satisfactorily in the United States between Baltimore and Washington, the lines extended in the three following years to Portland, Maine, and from New York, through Buffalo, to Montreal, Canada. In 1848, almost all United States had gotten to be interconnected, and in all directions new lines were projected. Soon the cities and towns of all the industrialized nations were connected by the telegraph, and in 1921 there were more than 2,400,000 kilometers of telegraphic lines, containing about 9,600,000 kilometers of wire.

In a long line, the current that circulates though the circuit is essentially weak, because of the high resistance of the many kilometers of wire. The signal , in addition, is weaker in the receiving end than in the emitting end, because of the considerable amount of current that passes from the isolated wire to earth and returns to the transmitting station, without reaching the resonator.

Morse and Continental alphabets

In order to overcome this difficulty Morse invented the relays, or repeaters, that were connected at regular intervals to the line. The relay consisted of an electromagnet device , that would attract its iron sheet puting in connection a battery with the following section of the line. With this device, a dispatch could be sent indefinitely .

Accelerating the transmission

The dispatches could be transmited between two stations by experienced operators with the simple Morse's telegraph at a máximum speed of 45 words per minute. When the traffic in the wire exceeded this proportion, it was necessary to increase the number of wires in the telegraphic line, or to devise some other method to increase the traffic in a wire . As the construction of telegraphic lines was expensive, it turned out to be economic to install in the ends of each line apparatuses that allowed a greater speed in the transmission. The Duplex telegraphic system, by which it could circulate dispatches in both directions at the same time, was suggested already in 1853 and began to practically work in 1868.

In the differential duplex system, when the person presses his manipulator that operates in A, he sends an equal amount of current in both directions from the central connection to his receiver. This last one , therefore, will not work; but the current directed in a single direction through the receiver in B will force this receiver to work. The operator in B, in a similar way can simultaneously send a dispatch to A by the same wire . A system of quadruple telegraph, invented by Thomas A. Edison , began to work in 1874, and reached the simultaneous transmition of four dispatches , two in each direction, by a single wire . Several of the circuits of the quadruple system were used in following years in most of the telegraphic lines. A sextuple system had been devised , that transmitted up to three dispatches in each direction simultaneously; but it did not become a common use.

Another method that allowed to transmit six dispatches in each direction at the same time demanded the installation of two revolving wheels of contacts, which turned at the same speed in each end of the line. Each operator was thus connected to the line and the corresponding receiver intermittently by means of similar contacts of the revolving wheels. By this system it was possible to send simultaneously 200 words per minute in each direction, which represented the highest speed of transmission by a telegraph system that worked by hand.

The increasing demand of the electrical telegraph for the transmission of long Press dispatches lead to the development of automatic systems, by which a speed of 400 words per minute in each direction with a single wire could be reached . In most of the automatic telegraphs that were in use in the 30's it was necessary to prepare beforehand the dispatch to transmit, operating in the keyboard of a special type of typewriter, that perforated the dots and dashes in a paper strip that ran through the machine. When this strip was finished, it was passed quickly to the emitting apparatus, that produced the corresponding current pulsations in the telegraphic line. In the receiving station the dispatch was registered on a movable tape, with similar dots and dashes , as in the primitive Morse telegraph, or by a printer machine to see the current pulsations translated in letters printed on a tape.

Photo : Western Union Tel. Co.

RECORDING SIPHON: This sensible instrument registered graphically on a paper strip, by means of a waved line, the dipatch sent throughout an underwater cable. A wave, throughout the mean line, represented a dash , and, to the other side, a dot.

A modification soon arose from this method in the " ticker " telegraph system , or electrical indicator of prices , by which an operator in the stock exchange , typed in a keyboard, and by telegraphic connection printed the prices of stock values on machine paper tapes in the stockbrokers office simultaneously in the offices of many cities.

Other applications of the telegraph
An instrument called "telantograph" extended the principle of the telegraph to the remote reproduction of the writing. In the receiving station the writing by means of a moving pencil reproduced electrically, copying faithfully what it was written with a similar pencil in the other end of the line. For the electrical transmission of drawings, call "telephotography", had also been devised several methods, that had reached a high degree of perfection. In every case a small ray of light was sent successively through every detail of the drawing that was to be transmited . The intensity of the light transmitted by the drawing in each point depended on the degree of light and shade of that point. When this transmitted light hit a small strip of selenium it changed its electrical resistance, so that the most intense was the light it was smaller the resistance of the selenium. In this way current pulsations could be sent by a wire successively to a receiver, where the original drawing could be reproduced, point by point, by the variable chemical action of the current on a sensible paper . A system had also been invented by which a painting with its original colors could also be reproduced. Numerous systems of television had been constructed depending on the same property of the selenium, which allowed simultaneously to see all the parts of an object by means of the aid of conection wires . In an occasion exhibited simple geometric models could be seen at 115 kilometers of distance, representing this fact a technological breakthrough for the science in those years.

The telegraphic fire calls allowed to press a switch in the nearest special box for these cases and notifying to the Firemen corps of the existence of a fire and its approximate location . In the automatic fire alarm the very heat of the fire tripped the bell sound.

The bell of the door transformed into a telegraph .
The hour signals sent daily at noon to the main cities of the United States from Washington allowed to syncronize by telegraph all the clocks in the country . In the railroads, steam powered as much as electrical, the telegraph has played a very important role, avoiding accidents and maintaining a continuous service. A system of signals, by means of color lights or by means of the positions of a semaphoric arm was used to inform of the situation of the road in front of a train. While these signals, in most of the cases, were obtained automatically by the movement of the trains, frequently they were under the strange government of an emitting train. Until the vulgar door bell was not but another simple application of the principle of the telegraph, developed with more care in the hotel indicator.

The submarine telegraph.
The transmission of telegraphic dispatches by an underwater cable through the ocean presented much greater difficulties than those ones found on earth. The laying and conservation of the cable itself supposed great difficulties and expenses. Every centimeter of the inner copper thread had to be perfectly isolated from the salt water that surrounded it. Its operation was slower than in the terrestrial line. In this last one, when pressing the manipulator the current grows quickly until its complete energy in all the parts of the line, practically, at the same time. In the underwater cable, the current raises quickly in the transmitting station; but it can spend more of a second in reaching the same magnitude in the receiving station located at 3,200 kilometers of distance. In addition the relay that was used at intervals to reinforce the signal in the terrestrial line could not be connected, for clear related reasons , in the underwater cable.
Although other people had suggested the underwater cable use in telegraphy, and even when a cable was layed in 1846 between England and France, the glory of the accomplishment of a transatlantic cable tended successfully was due to the indomitable spirit of a North American enterpreneur, Cyrus W. Field (1819-1892). After retiring of the active businesses, at the age of thirty three years, owner a great fortune, he met the inventor and Canadian electrician Frederic Newton Gisborne (1824-1892), who indeed had tended the first high seas cable in waters of the United States, between the Prince Edward Island and New Brunswick. and projected to link Cape Ray, Newfoundland and Cape Breton, Nova Scotia. Being interested in his project, Field considered the propitious occasion for another greater advance: a transatlantic cable. In 1856 he organized the Atlantic Telegraph Company, maintained almost entirely by English capital. With an English military ship and another American one he tried, in 1857, to tend a cable between Ireland and Newfoundland. The cable was broken at 536 kilometers of the coast of Ireland and was left. Another test was done in 1858, locating two military ships in the middle of the Ocean and loosening the cable as they sailed in opposite directions towards Ireland and Newfoundland. After having broken the cable several times, the ships returned to Queenstown. Later, in the same year the ships were located again in the middle of the Ocean and the cable was tended without accidents. In August 7 ,1858 the first signal from Newfoundland was sent to Ireland; but the cable stopped working the September 1 , 1858 and it was necessary to leave it, with great financial losses for the organizers of the company.

Another cable that was tended in 1865 broke at a distance of 1920 kilometers of Ireland and it could not be recovered. The following year was tended, happily, a new cable and it could be raised and be finished tending the cable that had been left in 1865. One of these cables stopped working in 1872 and other in 1877; but other four cables tended in the meantime continued in good condition. In 1921, the different parts from the world were linked by 530 underwater cables, with an overall length of 387,200 kilometers. The weakness of the signals transmitted through long cables demanded the invention of more sensible receivers. The recording siphon, invented by lord Kelvin in 1867, was used almost exclusively with this object at the beginning of XX Century. This instrument consisted of a light coil of fine isolated thread suspended between the poles of a powerful magnet. When the current of a cable circulated through the coil this one inclined to one side or the other one, according to the direction of the current. A thread tied to a point of the coil moved a small crystal tube containing ink to be placed next to one or the other edge of a paper tape that moved slowly under it. The other end of the crystal tube finished in an inkpot placed higher than the paper, so it transmitted the ink to the paper acting as a siphon. The current was sent from the transmitting station in a direction when it was wanted to represent a point,
, and in the inverse direction when it was wanted to represent a dash. When the waved line drawn on the paper passed over the horizontal line it was recognized as a dot, and when it passed underneath, like a dash, it was exclusively used the continental alphabet. The speed of transmission had been increased with a "duplex" system, that allowed to transmit two dispatches , one in each direction, at the same time. It had not been possible to adapt none of the fastest systems of the terrestrial lines to underwater cables.

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