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).
Trial of Bifocal dimming using dual-filament bulbs to avoid mechanical dipping mechanisms.
| Identifier | ExFiles\Box 61a\1\ scan0351 | |
| Date | 10th October 1928 | |
| Hs.{Lord Ernest Hives - Chair} from DA{Bernard Day - Chassis Design}/EV{Ivan Evernden - coachwork} 4477 DA{Bernard Day - Chassis Design}/EV{Ivan Evernden - coachwork}3/M10.10.28. BIFOCAL DIMMING. X.4477 X.1357. We are anxious to make a trial of this soon. It occurs to us that if you could obtain some Bifocal bulbs either American or English, we might try them in some Lucas 100 lamps by obtaining the double pole variety of holder, using both poles as the high potential leads, one to the main filament and one to the dipped, and a common earth return. We want if possible to avoid the mechanism involved by the mechanical dipping of reflectors or entire lamps. DA{Bernard Day - Chassis Design}/EV.{Ivan Evernden - coachwork} | ||