Assuming a train approaching from A, which has to continue on the main line past B on towards C, then the levers in the signal-cabin must first be pulled over to set the points 9 and bolt-lock 8 in proper position for the main line; and this operation will release the levers which have to be pulled over to lower the signals 5, 4, and 6, but at the same time will lock, and prevent the pulling over of the levers or lowering of the signals 2 and 1 for a train from A to B and D, or of the signals 14 and 15 for a train from D to B and A. The levers will, however, be free to pull over for setting the points 12 and lowering the signals 16, 17, and 13 for a train on the main line from C to B and A. In a similar manner, assuming a train approaching from D, which has to continue up to the main line at B and on towards A, then the lever in the cabin must first be pulled over to set the trailing points 12 in proper position; and this operation will release the levers which have to be pulled over to lower the signals 14 and 15, but at the same time will lock, and prevent the pulling over of the levers or lowering of the signals 5 and 4 for a train from A to B and C, or of the signals 16 and 17 for a train from C to B and A. The levers will, however, be free to pull over for setting the points 9 and bolt-lock 8 and lowering the signals 2 and 1 for the passage of a train on to the branch line from A to B and D. For a train from C to B and A, the levers 12, 16, 17, and 13 would be required, and these would lock levers 14 and 15, and prevent the approach of any train from D to B, but they would leave free the levers necessary either for a train from A to B and C, or for a train from A to B and D, but only one of them at a time, the setting of the one series locking the other series. A train from A to B and D would require the proper setting of the points 9, bolt-lock 8, and signals 2, 1, and 3; and these would lock 5 and 4, but would leave free the levers necessary either for a train from C to B and A, or for a train from D to B and A, but only one of them at a time. The cross-over road from the UP to DOWN main line, near the letter B 326 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.