Single Ended Halogen Capsule - M/32

The earliest tungsten halogen were made in the form of a linear quartz tube, pinched closed at both ends around an axial filament. While this arrangement was perfectly suitable for large area floodlights, they lacked the point-like nature of conventional lamps. Additionally, their production required the fabrication of two glass-to-metal seals, which were rather difficult and expensive to form at this time.

In 1961 the invention of the low voltage halogen capsule by J.G. Moore of Osram-GEC Wembley was published, in which both tails of a low voltage filament were pinched into a single seal to realise a remarkably compact new lamp. While Osram-GEC expanded its range to offer miniature halogen capsules to replace a number of photographic and projector lamps, another pioneer, Thorn Lighting, recognised the potential in general lighting mass markets. The single ended concept was ably exploited by Alex Halberstadt of the Enfield laboratories, and Thorn's first product was the 12V 50W capsule featured here, known in Britain as type M/32.

Thorn had already established a strong position in accent and display lighting, thanks to its earlier development of the low voltage incandescent reflector lamps. These offered tremendous performance increases over mains volt reflector lamps thanks to the higher efficacy and smaller size of the low voltage filaments, and it was a logical progression to shift to the 12V halogen capsules. From the 1970s onwards these began growing in popularity for high-end display lighting such as in museums and galleries. From the mid-1980s these capsules were cemented into a dichroic reflector, and produced by the millions as they dominated all aspects of retail and display lighting for several decades.
Manufacturer: British Lighting Industries Ltd.
Lamp Power: 50 Watts  
Lamp Voltage: 12 Volts  
Lamp Current: 4.16 Amperes  
Cap Type: GY6.35 Gold plated molybdenum
Bulb Type: T-10.5 T-3.5in eighths/inch
Bulb Finish: Clear Quartz
Filament Type: C-6 3.5 x 2.5mm
Atmosphere: Bromine in Ar
Luminous Flux: 900 lm  
Luminous Efficacy: 18.0 lm/W  
Peak Intensity: N/A  
Beam Distribution: N/A  
Colour Temperature & CRI: CCT: 3000K CRI: Ra 100
Chromaticity Co-ordinates: CCx: 0.452 CCy: 0.409
Rated Lifetime: 2000 hours to 50% survival
Burning Position: Universal  
Max. Overall Length: 44 mm 1 3/4"
Light Centre Length: 30 mm 1 3/16"
Factory: Tottenham, London United Kingdom
Date of Manufacture: April 1969 Date Code D9
Original / Present Value: GBP 18s 0d (1969) GBP £10.67 (2007)
References: 1) Thorn Lighting Comprehensive Catalogue, UK, 1969/70, p.CG13