||The concept of the Bumix-Mischlichtlamp was patented by Dr. Gunther Gläser of Geislingen, Germany, in 1949. In that same year these lamps were imported from Switzerland, possibly made under license by MEDA, a Swiss producer of special discharge lamps. In 1950 demand had risen to the extent that the Bumix Mischlicht GmbH was established in Geislingen, and extended its activities into the production of luminaires. It is not known whether this lamp would also have been produced in Germany, or continued to be imported from the original Swiss producer.
Whereas most mercury-tungsten lamps are designed with the filament connected in series with the arc to function as its ballast, in the Bumix lamps they are connected in parallel. The reason is to provide an increase in efficacy as well as to avoid the hot-restrike delay that can occur in cases of mains voltage fluctuations that cause the arc to extinguish.
Unusually for a mercury lamp, the arc tube has no auxiliary ignition electrode. Instant ignition is instead achieved by the special control gear, in which a capactor and bi-metal thermal starter provides an inductive voltage pulse from the ballast. A special 3-contact screw cap enables the filament to operate in parallel with this circuit, across a tapping of the ballast and hence at slightly lower voltage than the mains. The filament always operates to provide light, even while the arc tube is cooling down during a hot-restrike. Interestingly despite the high loading, the arc tube is fabricated from aluminosilicate hard glass rather than quartz. Seals are fabricated to molybdenum rods. Bumix lamps were made from 240-1350W with each different model being named after a celestial body.