Page:The Working and Management of an English Railway.djvu/89

 to all, combines them in a system incapable of discord."

There are several supplementary interlocking appliances now generally in use which may be briefly described. For instance, there is the "Facing-Point Lock," which is a bar of iron working in connection with facing points—that is, points by which one line diverges from another in the same direction. This bar, which is actuated by a separate lever in the cabin, works with, and securely locks, the points, and not until this has been done can the signal be lowered. The bar holds the points firmly in position, so that, even if the signal has been reversed, they cannot be moved while the train is passing over them. Then we have the "Locking Bar," somewhat similar to the facing-point lock, but actuated by the same lever that works the points. This is chiefly applied to siding points to prevent their being moved while a train is passing over them. "Detector Bars" are employed on parts of the line which cannot be seen by the signalman, to prevent the signals being lowered when the line is occupied by a train. "Detector Locks" are applied to facing points, and are worked by the wire that works the signals, and if the points should be injured or out of position the fault is at once detected, and the signal is locked at "danger."

Again, there is the "Point-rod Compensator," which automatically compensates for the expansion or contraction from heat or cold of the rods which actuate the points, and an "adjusting apparatus," which enables the signalman to adjust his signal wires without leaving his cabin, together with numerous other ingenious contrivances for working and interlocking with the signals the gates of level