33 RAILWAY CONSTRUCTION. 



In order to ensure that the points are in their proper 

 position before the signals are lowered, and to prevent the 

 signalman from shifting them while a train is passing over 

 them, all facing points must be fitted with facing-point locks 

 and locking-bars, and with means for detecting any failure in 

 the connections between the signal-cabin and points. The 

 length of the locking-bars to exceed the greatest wheel-base 

 between any two pairs of wheels of the vehicles in use on 

 the line, and the stock rails to be tied to gauge with iron or 

 steel ties. All points, whether facing or trailing, to be worked 

 or bolted by rools, and not by wires, and to be fitted with double 

 connecting-rods. 



6. The levers by which points and signals are worked to be 

 interlocked and, as a rule, brought close together, into the 

 position most convenient for the person working them, in a 

 signal-cabin or on a properly constructed stage. The signal- 

 cabin to be commodious, and to be supplied with a clock, and 

 with a separate block instrument for signalling trains on each 

 line of rails. The point-levers and signal-levers to be so placed 

 in the cabin that the signalman when working them shall have 

 the best possible view of the railway, and the cabin itself to be 

 so situated as to enable the signalman to see the arms and the 

 lights of the signals and the working of the points. The back 

 lights of the signal lamps to be made as small as possible, having 

 regard to efficiency, and when the front lights are visible to the 

 signalman in his cabin no back lights to be provided. The 

 fixed lights in the signal-cabin to be screened off, so as not to 

 be mistakable for the signals exhibited to control the running 

 of trains. If, from any unavoidable cause, the arm and light of 

 any signal cannot be seen by the signalman they must, as a rule, 

 be repeated in the cabin. 



7. The interlocking to be so arranged that the signalman shall 

 be unable to lower a signal for the approach of a train until 

 after he has set the points in the proper position for it to pass ; 

 that it shall not be possible for him to exhibit at the same 

 moment any two signals that can lead to a collision between 

 two trains ; and that, after having lowered the signals to allow 

 a train to pass, he shall not be able to move any points con- 

 nected with, or leading to, the line on which the train is moving. 

 Points also, if possible, to be so interlocked as to avoid the risk 

 of a collision. 



