Signal Department Drawings

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By Andrew Dickinson

SIGNAL DEPARTMENT DRAWINGS

BR(WR) Signal Engineers devised what I think was an excellent system to bring together all the diagrams that the Signal Dept. would use for a signal box into a logical and well-ordered book with an index. The GWR obviously had diagrams but it was perhaps not as well organised as the BR(WR) system and the diagrams were not as well detailed and lacked some of the information that the BR(WR) system had. Some of the tables devised by the BR(WR) were much improved over the GWR information and so made the job a lot easier when using the information to find a fault in the equipment.
The BR(WR) also devised the 'Centre Number' system whereby each signalling installation had its own reference number. At Exminster, this was 840 and on the drawings for Exminster, this is prefixed by 'S'. So all diagrams in the book would begin S840. The next signal box was Cotfield and this would have been S841 and so on.
The contents of the BR(WR) book was as follows:-

S840/1	Index (And Record of Amendments)
S840/2	Locking Sketch (Diagram of Track Layout with Signals, TCs, etc.)
S840/3	Locking Table
S840/4	Detection Table (Mechanical and Electrical)
S840/5	Electrical Control Table (Block, Electric Lock Controls, etc.)
S840/6	Locking Chart
S840/7	Lever Leads and Pull Plates
S840/8	Lever Lock and Contact Schedule
S840/9	Schedule of Repeaters and Indicators
S840/10	SB Internal Wiring (incl. Cables, Terminal Boards, etc.)
S840/11	External Equipment Wiring (incl. Signals, Points, Track Circuits, etc.)
S840/12	SB Diagram (incl. Illuminated Diagrams)
[S840/13	Colour-light Aspect Sequence Chart]
S840/18	Details of Locking Frame including frame dimensions and tappet details

This is the final part of Andrew Dickinsons series. On behalf of all the readers of this newsletter, may I thank you, Andrew, for providing us with this fascinating reading.