RAILWAY CONSTRUCTION. 333 



railway station, a siding which is too far away to be worked 

 direct from a signal cabin, and not sufficiently used to warrant a 

 separate cabin. Such sidings can be worked by a small ground 

 frame opened or locked by a special key attached to the inter- 

 locking machinery in the adjoining signal cabin on a double-line 

 railway, or attached to the train staff on a single line. 



Fig. 506 shows the arrangement applied to a double line with 

 the outlying siding turning out of the UP main line, the points 

 lying in a trailing direction for the running trains. Before the 

 special and only key can be withdrawn from its seat in the 

 interlocking frame of the signal cabin, all the UP main line 

 signals must be set to danger, and cannot be moved from danger 

 until the key is restored to its proper seat again. When the key 

 is removed from the signal cabin, it can be taken to the ground 

 frame at A, inserted in the key opening, and by turning it partly 

 round, will release the bar which locks the levers of the facing 

 point bolt-lock and the points. When these two levers are free 

 the points can be opened, and vehicles moved into or out of the 

 siding B C, but the special key cannot be withdrawn from the 

 ground-frame A, until the points and facing point bolt-lock are 

 put back again into their normal position for main line working. 

 When the operations at the siding are completed, the special key 

 can be removed, and taken back to its proper place in the signal- 

 cabin, and ordinary working be resumed. 



Fig. 507 shows the application of the detached locks on a 

 single line, and is a sketch of a portion of railway on which 

 there is a small station B, with a goods siding F G, where the 

 traffic is too small to require anything more than ground frames 

 and detached locks. An engine-driver before leaving the station 

 A, receives a train staff, which gives him possession of the line 

 as far as C, including of course the intermediate station B, and 

 this staff he must carry with him and hand over to the signal- 

 man on his arrival at the end of the section at C. At each of 

 the points D and E is placed a two lever ground frame, similar 

 to the one shown in Fig. 506, and attached to the train staff is a 

 key, which will operate either of the two ground frames, but 

 only one at a time, as the key must be inserted before the levers 

 can be moved. When the train is proceeding in the direction 

 from A to C, it will be more convenient to shunt vehicles into 

 or out of the siding F G, by means of the points E, but when 

 proceeding from C to A, the points D will be more convenient. 



