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Sylvania SHP-T Standby with Twin Arc Tubes |
The principal reason for the development is that when the electricity supply is restored after a momentary interruption, there is a second cool arc tube inside the lamp which can be illuminated instantaneously without delay. The hot arc tube which was in use beforehand cannot be ignited for several minutes until after it has cooled down, and in certain applications the delay may be unacceptable.
In addition, the fact that the lamp contains two arc tubes means that its service life can effectively be doubled. This is particularly useful in installations where maintenance is difficult.
However the lamp remains to become well accepted by street lighting agencies where maintenance costs are considerable. Partly this is on the grounds of the higher initial lamp price, but also it is found that this lamp does not function quite so efficiently in many of the more compact modern lanterns. To accommodate two arc tubes, they must be offset from the central axis of the lamp and consequently they can no longer reside at the optical centre of the reflector system. There can also be a not inconsiderable change in beam profile from one day to the next, depending on which arc tube happens to strike up first (a random event) .
Nevertheless, particularly in the low wattage sizes and where the lamp is employed for security lighting, the instant re-strike feature is invaluable and here it finds a sizeable market.
| Manufacturer: | GTE Sylvania | |
| Lamp Power: | 392 Watts | |
| Lamp Current: | 4.65 Amps | |
| Lamp Voltage: | 100 Volts | |
| Cap Type: | E40s/45 | Ni plated brass + vitrite |
| Bulb Finish: | Clear | Hard glass |
| Bulb Type: | T-46 | T-14½ in eighths/inch |
| Overall Length: | 280 mm | 11 inches |
| Light Centre Length: | 175 mm | 6¾ inches |
| Arc Length: | ||
| Electrodes: | Backwound Tungsten | Barium Calcium Tungstate |
| Atmosphere: | Na,Hg | Xe | Outer: Hard Vacuum |
| Luminous Flux: | 48,000 lm (@ 100 hrs) | 47,000 lm (@ 14,000hrs) |
| Luminous Efficacy: | 120.0 lm/W (@ 100 hrs) | 117.5 lm/W (@ 14,000hrs) |
| Colour Temperature & CRI: | CCT: 2050K | CRI: Ra 25 |
| Chromaticity Co-ordinates: | CCx: 0.520 | CCy: 0.420 |
| Burning Position: | Universal | |
| Rated Lifetime: | 28,000 hours | to 70% survival |
| Warm-up & Re-strike Time: | 5 minutes | Instantaneous restrike |
| Factory: | Arc Tubes: Shipley, UK | Lamp: Tienen, Belgium |
| Date of Manufacture: | 1988 | |
| Original & Present Value: | £60.13 (1989) | £100.22 (2005) |
