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A History of Wireless Telegraphy (2nd edition, revised), J. J. Fahie, 1901, pages 100-111:
T. A. EDISON--1885.
Electric communication with trains in motion, like communication with ships at sea and with lighthouses, has long been a favourite problem with electrical engineers: indeed it is much older of the two, and dates back to the first days of electric telegraphy.
In 1838 Edward Davy, the rival of Cooke and Wheatstone, proposed such a system. In a lecture on "Electric Telegraphy," delivered in London during the summer of 1838, he says:--
"I have a few words to say upon another application of electricity--namely, the purposes it will answer upon a railway, for giving notices of trains, of accidents, and stoppages. The numerous accidents which have occurred on railways seem to call for some remedy of the kind; and when future improvements shall have augmented the speed of travelling to a velocity which cannot at present be deemed safe, then every aid which science can afford must be called in to promote this object. Now, there is a contrivance, secured by patent, by which, at every station along the railway line, it may be seen by mere inspection of a dial what is the exact situation of the engines running either towards or from the station, and at what speed they are travelling. Every time the engine passes a milestone, the pointer on the dial moves forward to the next figure, a sound or alarm accompanying each movement.
"Not only this, but if two engines are approaching each other, by any casualty, on the same rails, then, at a distance of a mile or two, a timely notice can be given in each engine by a sound or alarm, from which the engineer would be apprised to slacken the speed; or, if the engineer be asleep or intoxicated, the same action might turn off the steam, independently of his attention, and thus prevent an accident." 63
In 1842 William Fothergill Cooke published his 'Telegraphic Railways,' descriptive of a crude system of train signals, which was tried, in 1843, in the Queen Street tunnel, Glasgow, and in the Clay Cross tunnel, Derby; and, on a more extensive scale, in 1844, on the Great Eastern Railway, between Norwich and Yarmouth.
Dujardin in 1845, Brett and Little in 1847, Edwin Clark in 1854, Bonelli in 1855, and many others, proposed various systems of train signalling; but as they are all based on ordinary telegraphic principles and require connecting wires, they do not specially concern us in this history.
Mr A. C. Brown, an officer of the Eastern Telegraph Company, claims to have been the first to suggest, in 1881, the method of induction for communicating with moving trains. In a letter published in the 'Electrician,' March 21, 1885, he says:--
"My objective was chiefly to provide an efficient means of fog-signalling, by enabling the signalman to communicate directly with the drivers or guards. I proposed to run a wire along the permanent way, parallel with the rails, and to wind a coil of wire round the engine, or carriage to be communicated with, in such a way as to get as long a length of wire parallel to, and as near to, the line-wire as possible, so as to be well exposed to the inductive action thereof. I then proposed to place in the signal-boxes a battery, signalling key, and rapid make-and-break instrument, or buzzer, and to thereby signal to the train, using a telephone in circuit with the train-coil as a receiver. By using an ordinary carbon transmitter in the line-wire, I also found it quite practicable to speak verbally to the train, so as to be distinctly heard in the telephone.
"This design was embodied in a paper which, in the year 1881, I laid before the managing director of the United Telephone Company, but want of time and opportunity prevented its being put into practice. It was experimentally tried at that time, using wire coils, properly proportioned in length, resistance, and distance apart to the conditions that would be obtained in practice. It has since been simplified and arranged to produce both visible and audible signals on the engine or car by induction from a No. 8 iron line-wire across a space of 6 inches, with a current of only one quarter ampère, or such as can easily be produced by the ordinary Daniell batteries used in railway work." 64
In 1883 Mr Willoughby Smith threw out a similar suggestion towards the end of his paper on "Voltaic-Electric Induction," read before the Institution of Electrical Engineers, November 8 of that: 65--
"Telegraph engineers," he says, "have done much towards accomplishing the successful working of our present railway system, but still there is much scope for improvements in the signalling arrangements. In foggy weather the system now adopted is comparatively useless, and recourse has to be had at such times to the dangerous and somewhat clumsy method of signalling by means of detonating charges placed upon the rails.
"Now, it has occurred to me that Volta-Electric induction might be employed with advantage in various ways for signalling purposes. For example, one or more spirals could be fixed between the rails at any convenient distance from the signalling station, so that, when necessary, intermittent currents could be sent through the spirals; and another spiral could be fixed beneath the engine, or guard's van, and connected to one or more telephones placed near those in charge of the train. Then, as the train passed over the fixed spiral, the sound given out by the transmitted would be loudly reproduced by the telephone, and indicate by its character the signal intended.
"One of my experiments in this direction will perhaps better illustrate my meaning. The large spiral was connected in circuit with twelve Leclanché cells and the two make-and-break transmitters before described. They were so connected that either transmitter could be switched into circuit when required, and this I considered the signalling station. The small spiral was so arranged that it passed in front of the large one at the distance of 8 inches, and at a speed of twenty-eight miles per hour. The terminals of the small spiral were connected to a telephone fixed in a distant room, the result being that the sound produced from either transmitter could be clearly heard and recognised every time the spirals passed each other. With a knowledge of this fact I think it will be readily understood how a cheap and efficient adjunct to the present system of railway signalling could be obtained by such means as I have ventured to bring to your notice this evening."
In 1885 Mr T. A. Edison had his attention directed to the subject, and with his usual thoroughness he soon produced a very complete system, with the assistance of Messrs Gilliland, Phelps, and W. Smith--to the last-named of whom the original idea is said to be due. 66
The inevitable avanbt-coureur appeared in the technical journals of the period, and as it is delightfully characteristic of the great magician of Menlo Park, we venture to reproduce it here: "Mr Edison's latest invention, an arrangement to telegraph from moving trains, is thus described by a recent visitor to his laboratory: Overhead was a board eight inches wide, suspended from the ceiling by ropes fastened to one of its edges. One side of it was covered with tinfoil, and was facing toward a wall 20 feet distant. 'That,' said Mr Edison, 'is my railroad signal; I make electricity jump 35 feet, and carry a message. This is something quite new; no induction has ever been known that extended over 3 or 4 or 5 feet. This invention uses what is called static electricity, and it makes every running train of cars a telegraph station, accessible to every other telegraph station on the road. Messages may be sent to and from conductors, and to and from passengers. It requires no extra wire, either under the cars or at the side of the cars, but uses the ordinary telegraph just as it is put up at the side of the track. This white board is a receiver and transmitter. A board like it is to be fastened lengthwise along the peak of each car, where it will be out of the way and will not be a blemish. When the train is telegraphed to, the message jumps from the wire on the side of the track and alights on this board, and is conveyed to the apparatus in the train below. It works beautifully from those wires strung yonder. I was as much astonished as anybody at finding out what could be done. It costs very little, moreover, as 300 miles of road can be equipped for 1000 dols.'"
This contrivance was patented in England on June 22, 1885, in the joint names of T. A. Edison and E. T. Gilliland, and is fully described in their specification, No. 7583, of which the following is an abstract:--
The object of the invention is to produce apparatus for telegraphing between moving trains, or between trains and stations, by induction and without the use of connecting wires. The accompanying drawing (fig. 9) represents a station and portions of two trains with the apparatus for signalling. The carriage to be used as the signal office has placed upon its top or side, or upon each side, a metallic condensing surface running the entire length of the car. This consists of a strip a of metal, say a foot wide, well insulated by blocks of glass; or it may be thin sheet metal or metallic foil secured to canvas, and similarly insulated from the body of the car. To increase the total condensing surface, all the carriages of the train are preferably provided with such strips, which are connected electrically by suitable couplings c when the train is made up. A wire 1 is connected with this condensing surface, and extends through the apparatus to the carriage-truck so as to form an earth connection through the wheels and the rails upon which they travel. The apparatus just mentioned consists of an induction coil B, the secondary wire of which is of extremely high resistance, and is in the circuit of wire 1, in which is also connected a telephone C of high resistance. This is preferably an electro-motograph telephone, the chalk cylinder of which is kept in constant rotation by a suitable motor, electrical or mechanical; but a magneto-electric or other suitable form of telephone may be employed.
In the primary circuit of the induction coil B are a local battery d and a revolving circuit-breaker D. This is a wheel having its surface broken by cross strips of insulation; upon it rests a spring, the circuit being through the spring to the spindle of the wheel. This wheel is kept in rapid motion by a suitable motor, electrical or mechanical, the current vibrations produced by it being a great number per second and audible in the telephone receiver.
The circuit-breaker is shunted by a back point key E, which, normally, short-circuits it and prevents it from affecting the induction coil. A switch F short-circuits the secondary wire of the induction coil when receiving, and is opened in transmitting.
The ordinary telegraph wires 2, 3, 4, 5, run on poles at the side of the track, and, grounded at their ends, are utilised collectively for conveying the signals. They form the other surface of the condenser (the strips on the carriages forming one surface), while the intervening body of air is the dielectric.
In signalling between trains, signals are transmitted by working the key E in the office upon one train. This causes static impulses at the condensing surface upon the carriages which affect the telegraph wires. These in turn affect the condensing surface upon the carriages of the other train, and cause impulses which are audible in the telephone.
At each signalling station I there is erected between the telegraph wires a large metallic condensing surface K (fig. 10). This may be attached to a frame supported from the telegraph poles or from separate poles. A wire 6 runs from this condensing surface to the station, where it is connected to ground through the same character of transmitting and receiving apparatus already described for the carriages.
Instead of using this condensing surface outside of the station, a separate wire (7, 8, 9, 10, fig. 9) may be attached to each telegraph wire (or to each of as many as it is desired to utilise) and run into the station, where it is connected to one side of a condenser L, of ordinary form. The other sides of the several condensers L are connected together, and by a common wire 11 to ground through the transmitting and receiving apparatus.
The telegraph wires are kept constantly closed for transmitting the induction impulses by shunting the regular Morse keys M by condensers N. These condensers do not interfere with the carrying on of the ordinary telegraphing over such wires, at the same time that they form constantly closed paths for the induction impulses independent of the working of the ordinary Morse keys. The ordinary Morse relay and sounder are shown at O and P respectively.
The stations being connected for railway signalling inductively with the line wires the same as are the trains, signals are received and transmitted by a station the same as by a train. The trains and stations are connected inductively with the line wires in multiple arc, so to speak, signals being transmitted by keys, circuit breakers, and induction coils, and received by telephones.
The signalling is conducted by Morse characters, or by numerical signals in accordance with an established code.
Speaking of the potentialities of his system, Edison, early in 1886, said: "The outcome is easy to predict. Special correspondents may, in the future, wire their despatches straight to the offices of their journals. Railway business will be expedited to a degree undreamt of as things are, and the risk of accidents will be largely diminished by knowing the position of trains and the cause of delay or accident, if any, at every stage of their route. Ships at sea, many miles apart, will be able to communicate by means of balloon-kites, soaring several hundred feet above their decks. Messages can be passed from ship to ship, and a casualty like that of the Oregon telegraphed to the nearest land. In times of war the applications of the air-telegraph system are obvious. Regions now remote from telegraphs could be brought within the civilised circle by means of mountain or forest stations equipped with the new apparatus. Even the man of business of the future may communicate with his employés as he journeys to and from his office, and save time or make money while he is literally on the wing. Not the least interesting feature of this new departure in telegraphy is the thought that, in its turn, it may be the harbinger of still more wondrous modifications of the system which has girdled the earth in a space inconceivably short when compared with that imagined by the fairy romancer who created Puck." 67
The Edison system for trains was first put in operation at Staten Island, U. S.; then, a few months later, on the Chicago, Milwaukee, and St Paul line; and by October 1887 it was established on the Lehigh Valley Railroad, as related in the following paragraphs:--
"The success of what is called 'railway train telegraphy' is now assured, and October 6, 1887, will be a red-letter day in the history of the electric telegraph. On that day a special train left Jersey City with about 230 members of the Electric Club and guests of the Consolidated Railway Telegraph Company, in order to witness the working of the system on the Lehigh Valley Railroad. The system is a combination of the best features of the inventions of Edison, Gilliland, Phelps, and Smith, and although the speed often reached the rate of about sixty miles an hour, messages were sent from and received on the train without difficulty, although the current or the 'induction' had to jump from the train to the line wires, a distance of 25 feet. About four hundred messages were sent as the train ran from Perth Junction to Easton, amongst them a rather long one from Colonel Gouraud to Mr John Pender in London." 68
"One of the most interesting triumphs of invention has been achieved on the Lehigh Valley Railroad during the snowstorms of the past winter in the United States. This railway for some months has been using on its trains the system of communication known as train telegraphy. The wire, being of steel, and stretched upon stout poles only 15 or 16 feet high, withstood the fury of the storm. The consequence was that all snowed-up trains on the Lehigh Valley Railroad kept up constant communication with the terminus of the road, could define exactly their position, and, in short, had all the advantages of perfect telegraphic communication." 69
Soon after this the system fell into desuetude, and for a very simple reason--nobody wanted it. Whatever "special correspondents" and "the man of business" in the future may require, they, apparently, prefer nowadays to be free from telegrams of all sorts "while on the wing."
A few years later Mr Edison took out a fresh patent for the application of his method to long-distance communications over sea and land. The 'Illustrated London News' of February 27, 1892, gives an abstract of the specification with illustrative drawings.
If, says Mr Edison, a sufficient elevation be obtained to overcome the curvature of the earth, and to reduce as far as may be the earth's absorption, signalling may be carried on by static induction without the use of connecting wires. For signalling across oceans the method will be serviceable, while for communications between vessels at sea, or between vessels at sea and stations on land, the invention would be equally useful. There is also no obstacle to its employment between distant points on land, but in this case, he says, "it is necessary to increase the height (by using very high poles or captive balloons) from which the signalling operations are conducted, because of the induction-absorbing effect of houses, trees, and hills." These poles, surmounted by "condensing surfaces," are of course very like Marconi's--especially his earlier contrivances, where "capacity areas" in the shape of square sheets or cylinders of zinc are shown.
63 See the writer's 'History of Electric Telegraphy', 1884, p. 407. The most perfect block system of the present day does not do anything like this. Davy's plan was actually patented by Henry Pinkus! See his patent specification, No. 8644, of September 24, 1840.
64 For another proposal of Mr Brown, see infra.
65 Compare also his remarks, 'Jour. Inst. Elec. Engs.,' March 23, 1882, p. 144.
66 Although I have not seen any acknowledgment of their indebtedness, Mr Edison and his coadjutors can hardly have been ignorant of Mr Willoughby Smith's very clear proposal, of which their contrivance is but the practical realisation. Given the idea, the rest was easy enough.
67 'Weekly Irish Times,' April 10, 1886.
68 'Public Opinion,' November 4, 1887.
69 Ibid., April 13, 1888.
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