GE Mercury-Tungsten Reflector Sunlight Type 'RS'

In 1941 GE introduced the first integral reflector sunlight lamp to feature a combination of both ultraviolet and infrared radiation, in the form of this so-called 'RS' model.

At its heart is a high pressure mercury-quartz discharge tube based on the slightly earlier Sunlight S-4 ultraviolet lamp, but combined with a tungsten filament which performs the dual role of electrically ballasting the arc tube and providing the therapeutic benefit of infrared radiation. That concept had originally been pioneered by GE's German affiliate, Osram, which had introduced its self-ballasted Ultra-Vitalux lamp in 1937. It was a logical step for GE to combine that with the convenience of a reflector bulb since it had recently developed the type RS-4 sunlamp, comprising the 100W mercury H-4 arctube in an R-40 reflector bulb made of UV-B transmitting glass. Two years after the introduction of this self-ballasted reflector lamp, Osram followed suit with its Ultra-Vitalux Reflector lamp in 1942.

In order to allow reliable ignition on the lower 120V mains, a small filament is provided inside the arc tube to create a source of electrons, and this is preheated for a few seconds and then disconnected by a bi-metal switch that is heated by the main ballast filament. The outer bulb is also unusual due to its introduction of a metal-film getter in the neck area. This is presumed to be a film of a metal such as titanium or zirconium, intended to act as a hydrogen getter and facilitate lamp ignition. The film has been unusually deposted by short-circuiting the main leadwires of the stem via a stout metal wire, which has clearly been heated to fusion temperature to flash off the vapour film during lampmaking.
Manufacturer: General Electric Company, U.S.A.
Lamp Power: 275 Watts ~105W in arc
Lamp Current: 2.5 Amps 3.2A during starting
Lamp Voltage: 110-125 Volts
Cap Type: E26s/25 Brass + vitrite
Bulb Type: R-125 R-40 in eighths/inch
Bulb Finish: Inside Frosted #776 borosilicate glass
Electrodes: Tungsten Coil Thorium strip emitter
Atmosphere: Hg | Ar Outer: Nitrogen
Luminous Flux: 3050 lm 9.1 Wrad 380-800nm
Luminous Efficacy: 11.1 lm/W
Colour Temperature & CRI: CCT: 5250K CRI: Ra17
Chromaticity Co-ordinates: CCx: 0.340 CCy: 0.385
Ultraviolet Flux in Beam: UV-A: 25.5% - UV-B: 12.5% - UV-C: 0.09%
Beam Distribution 50° to half peak intensity
Rated Lifetime: 1,000 hours (approx. 400 cycles)
Warm-up & Re-strike Time: 3 minutes 5 minutes
Burning Position: Universal
Overall Length: 175 mm 67/8 inches
Light Centre Length: N/A
Factory: Cuyahoga, NELA Park Cleveland OH, U.S.A.
Date of Manufacture: 1947 November Date Code: 95
Original Value: US$9.95 (1948)
References: 1) GE Large Lamp Catalogue, 1948 USA, p.30
2) GE Large Lamp Price List #2195, 1st July 1946 p.7
3) GE Large Lamp Price List, April 1953 p.11
4) Mercury Lamps - Operating Characteristics & Applications (GE Bulletin LS-103), 1947 USA