488
EXPOSITION AT VIENNA.
tlie levers and semaphores, wliich must be at "arrest” before it can be moved. Hence, if the engineers obey the signals, there is no danger of collision. Delay, and not danger, is produced by the neglect of the man in charge of the levers. Where there are switches, as in the case of a branch line, each switch is connected to the same lever as its semaphore, and the signal cannot be put at V line clear unless the switch is right. In the model shown at Vienna, there are also gates which close across one line of rails, as for instance, those running north and south, when trains are crossing east and west, and vice versa .
In electrical interlocking systems, the " circuit ” on which each semaphore is placed, is carried through the "points” of the other semaphores or switches, which must be closed in order that the first semaphore may be worked. Messrs. Siemens & Halske, have an elaborate apparatus on exhi-
N
W
6
a
bition at Vienna, in which each switch and its corresponding semaphore is connected to a sliding-bar and a lever at the junction station. By means of the electrical apparatus used in Siemens’ block-signals, no switch or semaphore can be moved until all the switches and semaphores on crossing tracks are placed at "arrest.” Mr. Pope’s electrical semaphore has been adapted to the interlocking system, the connections being made in the following manner :—
Plate XIX.
l • Line wires .
T - Qrcund wires.
A
All four semaphores, A A 1 B 13 1 , are arranged to stand red by the action of gravity, when no current is passing. The switch S being turned on the point a, gives the right of way