The lamp, once adjusted, does not require any readjustment, and, in fact, is built in such a manner as to avoid the presence of adjusting devices in it. The lamp also contains an automatic safety device for preserving the continuity of the circuit in case of accidental injury to the feeding mechanism or the carbons of the lamps. This is quite important when a considerable number of lights are operated upon one circuit wire, as a break in the circuit, due to a defective lamp, would result in the extinguishment of all the lights. With the safety device mentioned, such a break does not occur, but the flow of current is preserved through the faulty lamp.
By an exceedingly simple device upon the carbon holding rod, the lamps are extinguished when the carbons are burned out, and injury by burning the holders completely avoided.
The system is based upon the joint inventions of Elihu Thomson and Edwin J. Houston, for generators, regulators, and electric lamps, and also the patents of Elihu Thomson, in generators, regulators, and electric lamps; all of which are now operated and controlled by the Thomson-Houston Electric Co., 131 Devonshire Street, Boston, Mass.
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One of the causes which gives rise to induction in the telephone lines running along the Belgian railroads is that there are so many electric bells in the stations.
Mr. Lippens proposes as a remedy for the trouble a slight modification of the vibrating bell of his invention so as to exclude from the line the extra currents from the bell.
In one of the styles (Fig. 1) a spring, R, is attached at T to a fixed metallic rod, and presses against the rod, T¹. The current enters through the terminal, B, traverses the bobbins, passes through T, through the spring, through T¹, and makes its exit through the other terminal. The armature is attracted, and the point, P, fixed thereto draws back the spring from the rod, T¹, and interrupts the current; but, at the moment at which the point touches the spring, and before the latter has been detached from the rod, T¹, the electro-magnet becomes included in a short circuit, and the line current, instead of passing through the bobbins for a very short time, passes through the wire, T, the armature, and the rod, T¹, so that the extra current is no longer sent into the line.
[Illustration: FIG. 1.]
In another style (Fig. 2) the current is not interrupted at all, but enters through the terminal, B, traverses the bobbins, and goes through C to the terminal, B.
[Illustration: Fig. 2.]
As soon as the armature is attracted, the spring, R, which is fixed to it presses against the fixed metallic rod, T, and thus gives the electricity a shorter travel than it would take by preference. The current ceases, then, to pass through the bobbins, demagnetization occurs, and the spring that holds the armature separates anew. The current now passes for a second time into the bobbins and produces a new action, and so on. There is no longer, then, any interruption of the current, and the motions of the hammer are brought about by the change in direction of the current, which alternately traverses and leaves the bobbins.