Engineering Wonders of the World
Volume I

RAILWAY SIGNALLING. 231 Fig. 12.—INTERIOR OF SOUTH JUNCTION SIGNAL BOX, CREWE. ELECTRIC POWER SIGNALLING INSTALLATION. Compare this with Fig. 10 to appreciate the saving in space occupied by levers. was employed to move the points, but was replaced by air compressed to a pressure of 60 lbs. or 70 lbs. supplied from a common air main. The valves of the points and signals were opened and closed by electricity at low voltage sent over aerial wires. Other agents are employed also. There are the all-air at low pressure (15 lbs.), a hydraulic system, and several all-electric methods. Fig. 12 is a view of the interior of Crewe South Junction signal box, where, as in eight other boxes at Crewe, the points and signals are operated electrically. This Electrical ^QX con^a|ns 247 levers, and Locking Frames at the other end of the station has 266 levers. From these it will be judged into what a small compass the locking frames can be got, owing to the fact that, as the levers have nothing more to do than to open or close electrical circuits, they can be made small and placed close together. Less than half the length and considerably less width is re- quired, and, as a consequence, the signal boxes may be reduced greatly in size. This is a great convenience. Less land is needed, and the lines and sidings have not to be interfered with so much to find space for a big signal box. There are other advantages. One is that, as flexible wires replace rigid rods, for which a direct course is necessary, almost any posi- tion will do for the signal box. Furthermore, point rods, which take up a lot of room, are eliminated. At Boston Southern Terminus, Mass., U.S.A., this gave additional siding accommodation sufficient for sixty-seven American passenger cars ; and at Glasgow Central Station the Caledonian Com- pany were able to lay down an additional line over the Clyde Bridge.