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50 Watt
Sodium Discharge Lamps

Group "AL/2 VS"
Two Way 165o

Group "AL/1 HS"
Two Way 165o

GROUP "AL/2 VS" & "AL/1 HS"


For use with 50-watt Sodium Electric
Discharge Lamps in vertical and horizontal

(Patent Nos. 228294 & 426069)

ESLA, 17 Canterbury
Canterbury 17

general construction

The reflectors consist of one piece castings glazed with silvered glass facets, cut from flat sheet, embedded in a special atmospheric resisting cement. Each facet is set at the exact angle and is of a calculated size to produce the desired light distribution.

Material: Cast iron or Aluminium non-corrosive alloy.
Finish: Green or Aluminium. Other colours to order.
Tapping: ¾" gas thread as standard. Tappings to 1¼" to order.
Lamp Holders: Bayonet Cap.

approximate dimensions and weights

Type Approx Dimensions Approx Weight
"AL/2 VS" "AL/1 HS" "AL/2 VS" "AL/1 HS"
Length Width Height Length Width Height Cast Iron Aluminium Cast Iron Aluminium
Two Way 12¼" 11¼" 14½" 12¼" 13" 7" 22 lbs 10 lbs 14 lbs 6 lbs
Three Way 11¼" 11¼" 14½" - - - 20 lbs 9 lbs - -
Four Way 11¼" 11¼" 14½" - - - 20 lbs 9 lbs - -

technical description

The reflectors are designed to produce a light distribution of the required characteristics to ensure good uniformity of illumination and road brightness. The peak candle power is projected at an angle of 10o below the horizontal.

Group "AL/2 VS" employs a special patented method of light control by which the elongated light source is split into two imaginary sections, each reflector redirecting the light flux from the respective sections.

This optical design is such that the light from the discharge lamp is applied to the road with the maximum of utility, latitude, and precision. This reflector can be applied to all unusual road conditions (bends, intersections, etc.) with the same ease and efficiency as for a straight normal road.

Group "AL1/ HS" produces a light distribution suitable for normal and close spacings and wide roads. The maximum candle power intensity is not so high as with the double reflector but the width of the light spread is more adaptable to the conditions mentioned.

Both these reflectors greatly enhance the advantages of these new light sources in a very practical and economical matter.

mounting height

When considering the question of the height at which these lighting units may be erected, it must be remembered that although the rated wattage is only 50, the light output is approximately equivalent to that of a 200-watt filament lamp. We do not therefore consider it advisable to erect these units at a height of less than 17', although the Group "AL/1 HS" reflector might, with great care, be applied to a mounting height less than this figure.

angular settings

Group "AL2/ VS": THis reflector is available in all the various angles as scheduled on the Catalogue section dealing with the Group "AL" filament lamp reflector.

In addition, a very interesting modification may be adpoted in the case of three way and four way road intersections by which the light flux may be directed on to the various roads in approximate proportion to their traffic denisty and importance. This fexibility is effected by combining a three way upper reflector with a two way lower, or a four way upper with a three or two way lower.

For example, taking a simple case of a central suspension unit at a "T" intersection of exactly right angles; the branch road being of less importance than the straight through road; a 180o/90o/90o three way upper reflector might be combined with a 180o two way lower reflector. Thus there would be two pairs of reflector wings operating up and down the main road, but only one reflector wing projecting down the branch road. This is a very useful procedure where it is not desired to sacrifice the light on the main road too much for the sake of the side road.

Group "AL1/ HS": This reflector is mainly for the economical application of sodium lamps to the usual two way lighting, the vertical fitting being employed if desired for junctions.

technical service

The personal services of our technical staff at the works are at our clients' disposal at all times. They are prepared to visit a district in order to advise on all street lighting problems, also to inspect every individual lighting position to ascertain the correct reflector, or this latter work can be done reasonably well from plans.

They are also ready to carry out photometric tests on site, for which purpose they are equipped with the latest portable photometers available.

schedule of angles

Group "AL/2 VS"
Two Way Three Way Four Way















120o 120o 120o

130o 130o 100o
130o 110o 120o

135o 135o 90o
135o 112½o 112½o

140o 140o 80o
140o 130o 90o
140o 120o 100o
140o 100o 120o

150o 140o 70o
150o 130o 80o
150o 120o 90o
150o 95o 115o
150o 80o 130o
150o 70o 140o

155o 150o 55o
155o 135o 70o
155o 115o 90o
155o 102½o 102½o
155o 90o 115o
155o 80o 125o
155o 55o 150o

160o 155o 45o
160o 120o 80o
160o 105o 95o
160o 90o 110o
160o 80o 120o
160o 70o 130o
160o 60o 140o

165o 165o 30o
165o 145o 50o
165o 140o 55o
165o 125o 70o
165o 115o 80o
165o 112½o 82½o
165o 105o 90o
165o 97½o 97½o
165o 95o 100o
165o 90o 105o
165o 82½o 112½o
165o 77½o 117½o
165o 60o 135o
165o 45o 150o
165o 35o 160o

170o 145o 45o
170o 100o 90o
170o 95o 95o
170o 75o 115o

175o 115o 70o
175o 45o 140o

180o 125o 55o
180o 120o 60o
180o 110o 70o
180o 100o 80o
180o 95o 85o
180o 90o 90o
180o 80o 100o
180o 70o 110o
180o 65o 115o
180o 55o 125o
180o 30o 150o

185o 145o 30o
185o 80o 95o

190o 95o 75o
190o 90o 80o
190o 85o 85o
190o 75o 95o
190o 70o 100o
190o 55o 115o
190o 40o 130o

195o 130o 35o
195o 115o 50o
195o 100o 65o
195o 82½o 82½o
195o 75o 90o
195o 55o 110o
195o 40o 125o

200o 135o 25o
200o 100o 60o
200o 80o 80o
200o 70o 90o
200o 60o 100o

205o 90o 65o
205o 77½o 77½o

210o 50o 100o

215o 90o 55o

220o 65o 75o

225o 45o 90o

230o 75o 55o

90o 90o 90o 90o

100o 80o 100o 80o
100o 100o 80o 80o

105o 50o 102½o 102½o
105o 80o 85o 90o
105o 90o 65o 100o
105o 90o 75o 90o

110o 70o 90o 90o
110o 80o 80o 90o
110o 90o 70o 90o

120o 40o 105o 95o
120o 80o 70o 90o
120o 100o 90o 50o
120o 105o 40o 95o

121o 73o 100o 66o

125o 50o 105o 80o
125o 70o 90o 75o
125o 90o 80o 65o

130o 35o 125o 70o

135o 65o 95o 65o

140o 70o 55o 95o

145o 40o 120o 55o
145o 55o 75o 85o
145o 65o 70o 80o
145o 75o 85o 55o

165o 15o 155o 25o
Group "AL/1 HS"
Two Way