GEC SOX Miniature Low Pressure Sodium
Low Pressure Sodium lamps have superbly proven themselves as being ideally suited to night time security illumination as well as their traditional applications.  Philips invented the 18W size lamp which was rapidly adopted, but its lumen output was still to high for many applications where it could lead to glare.

Osram-GEC directed its efforts at creating an even smaller lamp and in the early 1980's, the tiny 10W lamp was put on the market.  Delivering 1000 lumens it was offered as an alternative to 1000lm 75W GLS incandescent lamps in the company's outdoor luminaires.  Unfortunately the relatively high cost of the system was often prohibitive, and in addition the 10W SOX is rather longer than GLS lamps and could only fit into certain luminaires.  It is for this reason that Thorn worked on the 6W SOX lamp also described in this section.

The GEC 10W lamp managed to achieve an efficacy of 100 lm/W which offered substantial energy savings over the GLS lamps it was designed to replace.  However in such low wattages it must be remembered that efficacy becomes less important - a saving of just 65W would take many years to pay back the cost of this lamp and ballast.

This lamp employs an indium oxide film on its 38mm outer jacket, and contains a simple U-shaped discharge tube with a nickel plated heat-reflecting disc at the end.  Later lamps also had sodium retaining dimples at the bend. The electrodes are made with transverse rather than axial coils, and the mount assembly is built around a mica disc.  The cap is a conventional B22d brass type with large diameter skirt, as employed on old-style linear fluorescent lamps.
Manufacturer: The General Electric Company of England PLC
Lamp Power: 10 Watts
Lamp Current: 0.20 Amps
Lamp Voltage: 55 Volts
Cap Type: B22d/36x26 Brass, Vitrite Insulator
Bulb Finish: Indium Tin Oxide Soda-lime glass
Bulb Type: Inner: TU-12 x 28 Outer: TD-38
Overall Length: 150 mm 6 inches
Light Centre Length: 95 mm 3¾ inches
Arc Length:
Electrodes: CCC-4 Black Tungsten BCT emitter
Atmosphere: Na | 98.5% Ne, 1.5% Ar Outer: Hard Vacuum
Luminous Flux: 1,000 lm (@ 100 hrs) 950 lm (@ 2,000 hrs)
Luminous Efficacy: 100.0 lm/W (@ 100 hrs) 95.0 lm/W (@ 2,000 hrs)
Colour Temperature & CRI: CCT: 1700K CRI: Ra-44
Chromaticity Co-ordinates: CCx: 0.574 CCy: 0.425
Burning Position: Verical Base Up ± 95°
Rated Lifetime: Not Published
Warm-up & Re-strike Time: 10 minutes Instantaneous
Factory: Shaw, Oldham England
Date of Manufacture: May 1986 Date Code TD
Original & Present Value: