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Updated: May 7, 2025
Gould, dated February 2, 1877, Edison makes a most vigorous and impassioned complaint of his treatment, "which, acting cumulatively, was a long, unbroken disappointment to me"; and he reminds Mr. Gould of promises made to him the day the transfer had been effected of Edison's interest in the quadruplex.
As a premise to an explanation of the principles involved it should be noted that the transmission of telegraph messages by hand at a rate of fifty words per minute is considered a good average speed; hence, the availability of a telegraph line, as thus operated, is limited to this capacity except as it may be multiplied by two with the use of the duplex, or by four, with the quadruplex.
How ludicrously cumbersome was such an instrument when contrasted with the Morse electro-magnetic telegraph of to-day, which requires but a single wire; or with the harmonic telegraph of Gray, which permits the simultaneous transmission of eight or more separate messages over a single wire; or with the wonderful quadruplex telegraphic system of Edison which permits the simultaneous transmission of four separate and distinct messages over a single wire, two in one direction, and two in the opposite direction at the same time; or with the still more wonderful multiplex telegraph of Delaney, which is able to simultaneously transmit as many as seventy-two separate messages over a single wire, thirty-six in one direction and thirty-six in the opposite direction.
The immense difficulties of reducing such a system to practice may be readily conceived, especially when it is remembered that the "line" itself, running across hundreds of miles of country, is subject to all manner of atmospheric conditions, and varies from moment to moment in its ability to carry current, and also when it is borne in mind that the quadruplex requires at each end of the line a so-called "artificial line," which must have the exact resistance of the working line and must be varied with the variations in resistance of the working line.
Harrington, in a memorable affidavit, "the inventive efforts of Mr. Edison were not confined to automatic telegraphy, nor did they cease with the opening of that line to Washington." They all led up to the quadruplex. Flattered by their success, Messrs.
The quadruplex was the tempting goal toward which Edison now constantly turned, and after more than a year's strenuous work he filed a number of applications for patents in the late summer of 1874. Among them was one which was issued some years afterward as Patent No. 480,567, covering his well-known quadruplex.
Although, as we have seen in a previous part of this book, his earliest fame arose from his great practical work in telegraphic inventions and improvements, there is no way in which any definite computation can be made of the value of his contributions in the art except, perhaps, in the case of his quadruplex, through which alone it is estimated that there has been saved from $15,000,000 to $20,000,000 in the cost of line construction in this country.
When a single message is sent from one station to the other, or when both stations are sending messages that do not conflict, only one battery or the other is connected to the main line; but with the quadruplex, suppose one of the operators, in New York for instance, is sending reversals of current to Chicago; we can readily see how these changes in polarity will operate the polar relay at the distant station, but why will they not also operate the neutral relay at the distant station as well?
Now put the other foot on the rheostat and let the left elbow gently rest on the deodorizer. Keep the rubber tube connecting with the automatic fog whistle closely between the teeth and let the right elbow be in touch with the quadruplex while the apex of the left knee is pressed over the spark coil and the right ankle works the condenser." Uncle Gilbert grunted.
Aside from other material advantages, it is estimated that at least from $15,000,000 to $20,000,000 has been saved by the Edison quadruplex merely in the cost of line construction in America. The quadruplex has not as a rule the same working efficiency that four separate wires have.
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