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 schematic of a battery-powered ignition system, showing the placement of the ballast resistance.
| Identifier | Morton\M11\ img182 | |
| Date | 1st May 1919 guessed | |
| DASHBOARD BALLAST RESISTANCE NON TREMBLER COIL LOW TENSION CONNECTIONS R.R. IGNITION (BATTERY) BALLAST RESISTANCE CARRIED UNDERNEATH COIL | ||