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).
Hand-drawn sketch of four circuit diagrams, labeled FIG 1 to FIG 4.
| Identifier | ExFiles\Box 163\6\ img012 | |
| Date | 30th January 1930 guessed | |
| 2, 2R, FIG 1., FIG 2, FIG. 3, FIG 4. | ||