The sodium discharge source is accepted as ideal for the lighting of traffic routes. Now, in the large 200 watt linear version, a source is available that meets the higher lighting levels demanded by the steadily increasing traffic on the roads. The lantern takes full advantage of the characteristics of this source providing an ideal distribution with the sharp run back above the peak now considered so desirable if glare is to be minimized.

Specification

Special Features. The 200 watt linear sodium lamp is a powerful source of light, if, therefore, glare is to be avoided the output needs to be very carefully controlled. Fortunately, the cross section of the arc is small (about 1" in diameter) so that good control can be obtained in a lantern of comparitively small cross section. In fact the Alpha Five lantern is only 7" deep, yet a sharp run back in the distribution above the peak is achieved, so that an actual installation is remarkably free from glare. The bowl is clamped to the canopy by four quick-release toggles. The seal is completed by a neoprene gasket. The lamp is held in the correct focal position by two substantial Bi-Pin lamp holders which support the lamp by the cap. The lampholders are spring loaded, allowing easy lamp replacement.

Optical System. The light from the source is controlled by a combined refractor-reflector system. The refractors direct light into the main beam and give an almost complete cut-off above 90°. The reflectors control the light emitted in all directions below the peak and provide a smooth transition from the intensity in the peak to the reduced value in the vertically downward direction.

Materials. The canopy of the lantern is an aluminium pressign with an internal aluminium support casting. The bowl, to which is cemented refractor panels, is formed from plastic sheet.

Finish. The canopy and reflectors are anodised, the reflector receiving a polishing and brightening processes. The plastic bowl is treated with an antistatic compound.

Installation. The end support has an entry for a 5½" length of 1¼" B.S.P. plain barrel. This is gripped by two 3/8" B.S.W. set screws situated inside the lantern. Wiring is brought to a porcelain terminal block. Cable clamp is provided.

Lamp. ATLAS 200 watt linear sodium lamp.

Catalogue Number.

PG 1200.