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 sheet for 1 1/4 and 1 1/2 value ballast resistance.
| Identifier | ExFiles\Box 168a\5\ img037 | |
| Date | 19th January 1929 | |
| E7C. X7720 19.1.29. 1 1/4 and 1 1/2 VALUE BALLAST RESISTANCE Specification. Pure nickel wire, gauge 32 S.W.G. 30 inches and 35 inches length per ballast respectively. EFC. | ||