Field Telephone Cables - a quick look.
Okay, Field Telephone Cables, a quick reference.
D.2 Mark IV - One tinned copper (30 SWG) and 7 hard tinned steel (34 SWG) strands, vulcanised rubber, braided cotton, black preservative compound. Weight 33lb./mile. Resistance 270 Ohms/mile. Obsolescent (1938)
D.2 Mark IV, twisted - two cables D.2 Mark IV, twisted together with a right hand lay of 12 inches. Each cable coloured blue, green or yellow.
D.2 Mark V - Strands as D.2 Mark V, insulation is pure rubber, cotton tape, braided cotton, black preservative compound.
D.2 Mark V twisted - as D.2 Mark IV twisted but with D.2 Mark IV* cable. Same colours used.
D.3 Mark VI - One tinned copper (28 SWG) and hard tinned steel (30 SWG) strands, vulcanised rubber, braided flax, red preservative compound. Weight 44lb./mile. Resistance 136 Ohms/mile.
D.3 Mark VI, twisted - two cables D.3 Mark VI, twisted together with a right hand lay of 12 inches. Each cable coloured light or dark red. Weight 88lb./mile.
D.8 Mark II - One tinned copper (28 SWG) and seven hard tinned steel (28 SWG) strands, vulcanised rubber, braided flax, black preservative compound. Weight 74lb./mile. Resistance 100 Ohms/mile.
D.8 Mark I, twisted - two cables D.8, twisted together with a right hand lay of 12 inches. Each cable coloured blue, green or yellow. Weight 148lb./mile.
D3 is normally issued to artillery units and if laid with care is almost as good as D.8; D.2 is used for temporary lines on account of portability but its resistance is high and insulation weak. For the latter reason ist must never be buried or laid in mud or water. All D.2 cables are obsolescent. (Notes on Electricity 1938.)
Telephone cables were not polarity marked because it didn't matter which way round they were connected. Some pairs did have different coloured insulation but that was more to aid identification than anything else.
If anyone wants the (nearly) complete list of field cables (from D.1 to D.10, plus the two Assault Cables and the various Quads), I mught be persuaded to compile a list.
Chris.
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