326 RAILWAY CONSTRUCTION. 



letter B on sketch, is only intended for use in case of break-down 

 or accidents, and the normal position of the points is to lie clear 

 for the passage of trains on the main lines. To use the cross- 

 over road, the whole of^the signals must first be set to danger 

 before the points 7 and 7 can be opened to permit the passage 

 of an engine or train from the one main line to the other. 



The starting signals 6 and 3 should be placed sufficiently far 

 away that the longest passenger or goods train may stand 

 between them and the clearance points at G and E. These 

 starting signals are of great service to train- working at junctions. 

 Supposing a main-line train from A arriving at B before the 

 section from B to C was clear, such train could be brought to 

 a stand at signal 6, and remain there while another train from 

 A was allowed to pass B, and proceed onwards towards D ; or 

 a branch-line train from A to D could be brought to a stand 

 at 3, to allow a main-line train to proceed onwards from A to 

 B and C. The starting signal 13 should be placed well in 

 advance of the cross-over road to control anything passing from 

 one line to the other. 



Fig. 499 shows the modern grouping of signals for an ordinary 

 single-line junction. The arrangement is almost practically the 

 same as for the double-line junction shown in Fig. 498, there 

 being the same four distinct sets of trains to be controlled, but 

 not any cross-over road. The signal-cabin is placed on the 

 main line, a little in advance of the facing points, and a well- 

 fenced-in gangway, the same height as the engine footplate, is 

 carried out the proper distance from the rails, on which the 

 signalman can stand to hand over or receive the train staff from 

 the engine-driver when passing. 



At stations and places where there are several sidings and 

 lines connecting with the main lines, at considerable distances 

 apart, it will be necessary to have two or more signal-cabins 

 placed in suitable positions, not only for expediting the working 

 of the constant shunting movements, but also to insure that 

 there is a signal-cabin within the regulation distance of all 

 facing points on the main line. So far as the main line is 

 concerned, the interlocking of these cabins must be connected, 

 the one with the other, by slotting, or co-acting gearing, in such 

 manner that the cabin in advance shall always be able to 

 control the cabin in the rear in the lowering of the main-line 

 signals for an approaching train. Fig. 376 is a diagram sketch 



