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EXPOSITION AT VIENNA.
Plate XI. illustrates the appearance and working of the apparatus.
The external appearance of the semaphore is shown in Fig.
A. It is placed on a post at the right-hand side of the track, at a suitable height from the ground ; the signal is exhibited through two openings, each twelve inches in diameter, covered with glass, and illuminated at night by a lamp fitted with a reflector at the back of the signal-box.
The interior mechanism of the semaphore is shown .in Fig.
B. D is a disc about thirty inches in diameter, divided into four quarters, alternately white and red. An adjustable counter-weight, W, attached to the periphery of the disc, keeps it in the proper position to show red, indicating danger, except when under the influence of the electric current. Thus a white signal can only be shown when the machinery and battery are in perfect working order.
The disc is made to turn through one-fourth of a revolution by means of an electro-magnet M, the armature of which is attached to the short arm of the angular lever L, having a fulcrum at l. The long arm of this lever is connected by the pitman P with the crook K on the axis of the signal-disc. Thus the disc will turn and show a white signal whenever the magnet M is charged by the electric current. X is a supplementary magnet for locking the signal in position, when set white, as hereinafter explained.
The apparatus at the station may be at any required distance from the semaphore. It consist of a secondary or station-signal, which in principle and external appearance is a miniature copy of the distant semaphore—a differential relay, a signal-switch for operating the semaphore, and a main and also a local battery. In most cases a portion of the main battery may be employed to do the work of the local.
The operation of the apparatus is as follows : If it is desired to set the distant semaphore while , the signal-switch is turned on the stud m; a circuit is thus formed from the main battery through the switch, wire 1, magnet R of the differential relay, wire 2, semaphore magnet M, wire 3, circuit charger 4, and wire 5. The magnet R attracts its armature strongly, bringing the lever J into contact with B, and then forcing,the latter against the stop e, so that the local circuit,