Looking closely at his website, he has mistakenly listed the lamps as SO/V when the catalogue just states that the SO/H lamp is burned vertically cap up.
Here is the link for all this information:
http://www.simoncornwell.com/lighting/glossary/index.htmWhen I took a look at his glossary, he did state that SO/V was an official designation. See here:
so : light source : low pressure sodium, one cap
Designation of the first sodium lamps, invented by Philips in 1932. The first trial installation was along a road in Eindhoven, Holland (see below). At first the authorities were hesitant about the colour of the lamp and dared not use it. But Dr. A. F. Philips agreed to install the trial installation, and if it wasn't pleasing, Philips would take it down, paying all costs.
At first, there was much laughter about the "queer yellow lamps" but motorists soon realised their benefits (good visibility, less glare, better performance in fog). Therefore the trial installation was kept
The first installation in the UK was in Purley Way, Croydon, outside the airfield, also in 1932 (see below). This was probably prompted by the successful trial of the GEC's MA discharge lamp in East Lane, Wembley, early in the year.
It appeared that this first installation (100W DC) was installed in bucket-type cut-off lanterns. It lasted four years before being replaced with a larger installation of Wardle Liverpools on a catenary system, which lasted until the 1970s.
The bulb was typified by a two piece construction - the inner arc tube was enclosed in an outer tube which comprised a Dewar flask. When the inner tube was spent, it was removed and replaced - the outer tube, which was expensive to construct, was retained.
The Dewar vacuum chamber provided thermal insulation, allowing the inner tube to reach its optimum temperature of 260oC.
The original wattages and efficiencies were:
Watt Rating.
Total Nominal Lumens.
50
2550
70 (later 65)
3780
100
6100
150
9600
Philips sold the bulb under the Philora name - technical information can be found here.
On the 15th Novemebr, 1938, ELMA reclassified the wattage and efficiencies as follows:
Watt Rating.
Total Nominal Lumens.
Initial Nominal Efficiency.
Lumens/Watt.
Nominal Average Efficiency thoughout life
Lumens/Watt.
45
2500
55.5
42
60
3900
65.0
49
85
6100
71.5
57
140
10000
71.5
57
By the early 1960s, the efficiencies of the lamps had improved:
Watt Rating.
Inital Lamp lumens.
Average output throughout life.
85
6200
5525
140
10250
9100
The orientation of lamp burning was also important, and several designations were used:
/V Vertical cap up
/D Vertical cap down
/H Horizonal
/U Universal
The lamp was superceeded by the SOI design
Watt Rating. Total Nominal Lumens.
50 2550
70 (later 65) 3780
100 6100
150 9600
Watt Rating. Total Nominal Lumens. Initial Nominal Efficiency.
Lumens/Watt. Nominal Average Efficiency thoughout life
Lumens/Watt.
45 2500 55.5 42
60 3900 65.0 49
85 6100 71.5 57
140 10000 71.5 57
Watt Rating. Inital Lamp lumens. Average output throughout life.
85 6200 5525
140 10250 9100
