||Whereas most manufacturers initially developed their mains voltage single ended halogen lamps to replace incandescent lamps of 60-150W, Osram started an important trend by addressing the requirements for higher power lamps. This Halostar Single Ended range therefore comprised only the 150W and 250W ratings. The combination of small size and high output made them especially popular for high power downlights, as well as in compact spotlights for indoor accent lighting. Thanks to the small size of the filament it is possible to achieve rather good optical control.
The original version of this lamp had a full glass construction, but in the late 1980s it was superseded by the version featured here which employs a ceramic structure. It is understood that the introduction of the ceramic base enables more precise positioning of the inner halogen capsule with respect to the E27 cap, and as a result more consistent optical performance from the complete luminaire. Owing to the relatively high cost of such ceramic parts, it is unlikely that it would have been introduced to enable a cost reduction.
The capsule is bromine-filled to achieve high efficacy and universal burning. The filament is mounted in an especially compact arrangement, supported by three wires held in a single quartz bridge. Its coiled tails are hooked over the ends of the leading-in wires via an ingenious method which avoids the requirement for welding. The outer bulb provides protection and UV filtering and is also cemented to the ceramic base. Double glass fuses inside the capsule extension tube are employed to reduce the risk of explosion at end of life and hence permit operation in open luminaires.