There were many versions of the Holophane Prismalume available. These included the PS & PRSL (which were open-type luminaires) and the EP, PE & EGH (which were enclosed). They could acommodate 150W-400W high-pressure sodium, pulse-start metal halide or metal halide, but some were known to house 90W Cosmowhite (CPO-TW) lamps. The ballast housing was made from diecast aluminium, finished in white as standard, but corrosion resistant finish was an option for the PS & PE versions.

Derby

In Derby are a few of the 90W Cosmowhite (CPO-TW) versions, lighting the platforms around the Train Station.

They use flat-glass lenses.

I have been to Derby countless times, and I have caught them working on many occasions: