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).
Electrical resistance required for dimming side and tail lamps.
| Identifier | ExFiles\Box 61a\2\ scan0239 | |
| Date | 7th March 1934 | |
| Dimming of Side and Tail Lamps. 86/16. In a circuit having three lamps the total current in circuit is 1 ampere, of course this is its virtual value assuming 4 watt lamps are used. It was noticed that during tests the wattage varied about ± 8% from its virtual value on this type of lamp (Osram-). This therefore explains why, on putting a resistance in the circuit for dimming purposes the brilliance of the lamps were uneven. The most effective brilliance was obtained at .7 amperes, or .233 amperes per lamp, below this current the illumination fell off to almost nil. Thus the necessary resistance required is 10 ohms in the main circuit or 30 ohms in each branch circuit. RB{R. Bowen} 7.3.34 | ||