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 diagram of a battery ignition system showing the ballast resistance mounted underneath the coil.
| Identifier | ExFiles\Box 181\M11\ img182 | |
| Date | 1st May 1919 guessed | |
| DRS42/V2 BALLAST RESISTANCE NON TREMBLER COIL LOW TENSION CONNECTIONS TO L.A. RR. IGNITION (BATTERY) BALLAST RESISTANCE CARRIED UNDERNEATH COIL | ||