Sylvania Mercury-Tungsten Reflector Sunlight '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 the 'RS' model. Within a few years this improved variant was introduced by Sylvania.

At its heart is a high pressure mercury-quartz discharge tube based on the Sunlight S-4 ultraviolet lamp, 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. GE combined that with the convenience of a reflector bulb made of UV-B transmitting glass.

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 Sylvania lamp improved the mixing of the infrared from the filament and the ultraviolet from the arc by changing from a single-coil filament situated well beyond the focal point of the reflector, to a coiled-coil filament whose position is brought much closer to the centre of the arc. Another problem with the early RS lamps was the tendency for the mount assembly to shift off-centre during transportation damage, resulting in a non-uniform beam. The Sylvania RS design employs an unusually shaped RT-40 glass bulb whose large protruberance from the front provides robust support for the internal assembly.
Manufacturer: GTE Sylvania
Lamp Power: 275 Watts ~105W in arc
Lamp Current: 2.5 Amps 3.2A during starting
Lamp Voltage: 115-125 Volts
Cap Type: E26s/25 Brass + vitrite
Bulb Type: RT-125 RT-40 in eighths/inch
Bulb Finish: Inside Frosted #776 borosilicate glass
Electrodes: Tungsten Coil Double carbonate emitter
Atmosphere: Hg | Ar Outer: Argon-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: 300 hours 1200x 15-minute cycles
Warm-up & Re-strike Time: 3 minutes 5 minutes
Burning Position: Universal
Overall Length: 191 mm 71/2 inches
Light Centre Length: N/A
Factory: Manchester, N.H. U.S.A.
Date of Manufacture: 1966 March Date Code: 6308
Original Value: US$9.95 (1968)
References: 1) Sylvania Standard Price Schedule, 29 September 1950 - RS lamp not yet listed
2) Sylvania Standard Price Schedule, 1 November 1954 - RS lamp first known listing
3) Sylvania Large Lamp Price Schedule, 1 July 1959 p.20
4) Sylvania Large Lamp Catalogue, 1968 August, U.S.A., p.21
5) Sylvania Large Lamp Catalogue, 1973, U.S.A., p.37
6) Mercury Lamps - Operating Characteristics & Applications (GE Bulletin LS-103), 1947 USA