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 of a 327 typical double-line roadside station with two signal-cabins. The NORTH cabin has to work the signals and points in connection with the goods-shed, goods-sidings, and market branch, and the SOUTH cabin, those in connection with the coal and cattle sidings; and each of the cabins to work the signals and points of that portion of the main line adjoining its own cabin. For siding working, each cabin is quite distinct and independent of the other, but for main-line working the lowering of the signals can only be effected by the joint operation or co-acting of both cabins.