47)--by a short rod. The pin is situated
at such a distance from the axle of the cog wheel that a quarter of a
revolution suffices to move the points over. The points motor must, of
course, have its separate connections with the "central station." To show
how the points lie, the rod R also operates a semaphore with a double arm
(Fig. 46), one end of which is depressed--indicating that the track on that
side is open--when the other is horizontal, indicating "blocked." The arms
point across the track.
[Illustration: FIG. 45.--Points for electric railway.]
Details.--The tongues must be bevelled off to a point on the sides
respectively nearest to the continuous rails. The parts AA are bent out at
the ends to make guides, which, in combination with the safety rails, will
prevent the wheels jumping the track. Care should be taken to insulate
centre rail connecting wires where they pass through or under the wheel
rails.
It is advisable to lay out a set of points, together with motor and
signals, on a separate board.
[Illustration: Fig. 46.--Double-armed signal, operated by points.
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