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Osram 280W Twin-Tube SOI/H |
Introduced in 1959, the primary purpose of this lamp was to offer high light output from existing 140W lanterns - it is much shorter than Philips' 5-foot long 300W SOI alternative. It also offered streetlighting authorities the opportunity to reduce electricity consumption as road traffic volumes eased late into the night, by simply switching off one discharge tube and therefore halving power consumption. Alternatively if both discharge tubes are connected in parallel, only one will ever strike up, and it was possible to double the lamp maintenance period by equipping each lantern with an auxiliary discharge tube - albeit with a small drop in efficacy.
Perhaps because of the expense of this lamp, or the fact that there was insufficient room to incorporate any heat-reflecting glass sleeves to boost efficacy, or simply because of its complexity, fragility and considerable weight, it never achieved widespread acceptance. Its requirement for two ballasts and duplicated wiring would also have added to the installation expense, and GEC decided to cease manufacture of this unusual product around 1969. This lamp is one of only five known examples still in existence.
| Manufacturer: | The General Electric Company of England PLC | |
| Lamp Power: | 280 Watts | |
| Lamp Current: | 2x 0.9 Amps | 2x 0.81A Starting Current |
| Lamp Voltage: | 2x 160 Volts | 2x 450V ignition |
| Cap Type: | UX4 | British 4-Pin Valve |
| Bulb Type: | T-65 | T-20½ in eighths/inch |
| Bulb Finish: | Clear | Soda-lime glass |
| Electrodes: | CCC-4 Beehive | Black W + BCT emitter |
| Arc Length: | ||
| Atmosphere: | Inner: Na | NeAr0.8% | Outer: Hard Vacuum |
| Luminous Flux: | 19,000 lm (@ 100h) | 16,800 lm (average) |
| Luminous Efficacy: | 67.9 lm/W (@ 100h) | 60 lm/W (average) |
| Colour Temperature & CRI: | CCT: 1700K | CRI: Ra -44 |
| Chromaticity Co-ordinates: | CCx: 0.574 | CCy: 0.425 |
| Rated Lifetime: | 6,000 hours | 70% survival |
| Warm-up & Re-strike time: | Approx. 15 minutes | Instantaneous |
| Burning Position: | Horizontal ± 20° | |
| Overall Length: | 519 ± 10 mm | 20¾ inches |
| Light Centre Length: | 280 ± 10 mm | 11 inches |
| Factory: | Shaw, Oldham | England |
| Date of Manufacture: | October 1958 | Date Code PL |
| Original / Present Value: | £7 18s 0d (1959) | £164.10 (2014) |
