It wasn’t until the early 1960s that General Electric (GE) cracked the problems, closely followed by the GEC and Philips. A prototype high pressure sodium lamp was exhibited at the APLE's annual conference in 1963, but it wasn’t until 1966 that the GEC erected an experimental installation along East Lane, Wembley (which, incidentally, also saw the first experimental medium-pressure mercury installation over thirty years before).

The first commercial installation in the UK was erected along the Southend ring road, but it was the City Of London who gained the most recognition by beginning a radial upgrading of all their lighting to high pressure sodium in 1967. As the early HPS bulbs were designed to be retrofitted into existing mercury installations, the lanterns chosen by the City Of London were slightly modified versions of existing mercury lanterns.

The first true HPS lanterns (designed from scratch with the new light source in mind) appeared in the late 1960s and early 1970s. All these lanterns utilised a cross-over design: whilst this was an adaption of existing mercury lanterns, it also moved the lamp up into the lantern’s canopy (where it could not be directly viewed by drivers, thus minimalising the glare) and allowed designs to cater for both cut-off and semi-cut-off.

Wider adoption of high pressure sodium was stalled by the energy crisis, as it couldn’t match the efficiency of its low pressure sodium brother. Councils, believing in the simple maximum lumens per watt paradigm, replaced existing tungsten, mercury and fluorescent schemes by low pressure sodium. So it wasn’t until the 1990s that HPS started appearing in greater quantities.

With its efficiency between high pressure mercury and low pressure sodium, HPS became even more attractive when LPS was finally exorcised from the British Standards of street lighting (as it didn't provide an adequate colour rendering). However, it didn't remain as first choice for new and replacement lighting schemes for long. Renewed interest in fluorescent (from compact fluorescent sources), the emergence of affordable metal halide and the possible introduction of LED have all questioned the automatic selection of high pressure sodium for schemes.

Therefore by the end of the first decade of the new century, high pressure sodium’s position as the natural choice for street lighting was coming under pressure.

Name: GEC Z8832/70
Date: Mid 1970s -
Dimensions: Length: 54cm, Width: 27cm, Depth: 18cm
Light Distibution: Cut-Off (BS 4533 Part 2)
Lamp: 35W SOX, 80-125W MBF/U, 50-70W SON

The secondary optical system comprises a white plastic over-reflector mounted above the bulb which reflects light emitted above the bulb back towards the street surface.

When opened, the cover plate swings open and all the gear is mounted on its opposite site. Three components are usually screwed to the cover plate: the main lamp choke, a power correction capacitor and an ignitor.

facing profile I can't recall the provenance of this lantern. However, it was installed somewhere as the lantern has been modified and repaired whilst in service.

front profile The bowl is held in position by a single stainless steel clip.

trailing profile The lantern was painted white whilst in service. Normally this wouldn’t be necessary as the canopy is made from Glass Reinforced Plastic (GRP). Some possible reasons for the paint include: an attempt to waterproof the lantern after the GRP became porous (a known problem with some later GEC GRP low pressure sodium lanterns); protection against flaking glass fibres (a known problem with several lantern types); or slightly over-zealous restoration by a collector.

canopy The GEC usually embossed their logo on the canopy of their lanterns but it's surprisingly absent from the Z5530 range.

logo Additional marks and scuffs suggest the lantern was painted whilst in service and it wasn’t a post-removal restoration. (Incidentally note the black insulation tape over the photocell; this allowed me to turn on the lantern in the daytime).

pedestrian view This classic view clearly shows the two reflectors positioned either side of the bowl. The gear compartment plate also carries a servicing warning message which became standard for many of the GEC’s lanterns produced in the 1980s.

vertical The bowl is simply clear and doesn't carry any additional refractors.

interior #1 The secondary optical system comprises a simple white plastic sheet screwed into the canopy of the lantern. Such an addition is questionable, particularly in a white plastic lantern, but perhaps the range was available in different colours, so a white over reflector was added as standard. The lantern bares the number "ZD 6048" on the canopy under this cover. This was a GEC classification code and is the only reason I believe this was a GEC lantern (and not the later Siemens or Whitecroft models).

interior #2 The gear compartment is now a mess and suggests the lantern has been repaired several times in service. The original choke and power correction capacitor have gone. Their replacement is an Italian MagneTek choke for 70W SON. The Paramar ignitor is probably the only original component still in-situ. The installation of the new gear has not been done well and the terminal strip connector is now loose in the gear compartment (it should be screwed to the lug near the photocell). It will be tidied up in the future. The lantern's identification sticker is also missing. This was originally stuck in the square shaped area on the gear compartment tray next to the ignitor.

This was one of the last lanterns designed by the GEC; of cut-off, reflector design, it catered for the introduction of the SON-E lamp, but could also take mercury or low-pressure sodium.