The LMS, LNER and SR introduced upper quadrant signal arms in the late 1920s. At first, the arms were of the corrugated steel pattern, but this changed around 1936 to the plain type. These signal arms were used for all new installations, and also gradually replaced the lower quadrant arms on signals inherited from the relevant pre-Group companies (a process that is still not complete!). BR adopted the design, and new semaphore signals are still being installed today, where replacement by colour lights is inappropriate.

All three companies began by installing the arms on wooden (S006, S0017, S0028) and lattice steel (S002, S0022, S0023, S0041, S0042) posts and dolls. Concrete posts (S0018) were also used, particularly on the LNER. In the 1930s, the LMS and LNER switched to tubular steel posts (T564, T250), whilst the SR began making posts from bolted lengths of scrap rail (S0032). BR continued these designs.

This pack of two ex-D&S frets supersedes S0012. The arm fret was formerly 300SA, and the fittings fret 250PF.

The actual sizes of the frets are 41½ x 49½mm (arms) and 42 x 50mm (fittings); they are etched in 0.012" brass.

Identification and quantity of components on the frets:
1. Plain distant arm (1)
2. Plain home arms (5)
3. Corrugated home arms (2)
4. Plain miniature arms (2)
5. Back-blinders (8)
6. Operating wire lugs (10)
7. Rule 55 fireman's call plunger plate (1)
8. Rule 55 track circuit diamonds (4)
9. Washers (51)
10. Balance lever bracket backplates (7)
11. Balance lever bracket jaws (7)
12. Balance levers (7 in two sizes)
13. Balance weights (21 in two sizes)
14. Crank brackets (8)
15. Cranks (10 in two sizes)

To see exactly what is involved in using these parts, download the instruction sheet as an Adobe Acrobat® file (139kb).