From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Specification for 1¼ and 1¾ value ballast resistances.
| Identifier | ExFiles\Box 168a\5\ img035 | |
| Date | 19th January 1929 | |
| X7720 19.1.29. 1¼ and 1¾ VALUE BALLAST RESISTANCE Specification. Pure nickel wire, gauge 32 S.W.G. 30 inches and 35 inches length per ballast respectively. EFC. | ||