Championing the low-pressure sodium (SOX/LPS) lamp.

Introduction - Advantages - How to buy (new & second-hand) - Resources - Your views

SOX streetlight in Wrexham, U.K. SOX lamp warming up from cold

Left: Thorn Beta 5 (35W) in Wrexham, May 2004. Middle - GEC Z9454 warming up. Right: M60 motorway near Manchester, U.K., August 2018, reproduced with permission from Callum Fraser.

Low-pressure sodium lamps (SOX or LPS lamps) are destinctive for shining with a golden yellow light, as shown in the photo on the left. They are also an energy source with very high energy efficiency. They have several applications but are most commonly used in streetlighting - in fact they have been used in streetlighting in the United Kingdom and in various places around the world since the 1930s. However, they can also be used in science laboratories, security lighting, or simply as a novel lighting source. Its yellow light is caused by the sodium that is used within the lamp. When the light switches on, it glows red, and slowly warms up to yellow over the course of a few minutes, as shown in the sequence of photos below.


Although many areas of the UK still use SOX lighting on streets and other roads, it is currently in decline, often a victim of misinformation about its merits and drawbacks. A SOX light in fact has many advantages:

1. As mentioned above, SOX lights are very efficient in their use of energy.
2. They are more effective in rain, fog and snow as the light does not become blurred by passing through raindrops etc.
3. High contrast recognition: Although the colour rendering of a low-pressure sodium lamp is poor, the contrast between light and dark is very good.
4. It has a relatively low operating temperature, meaning it can be used with cheaper components.
5. The light pollution it causes is easier for astronomers to filter out because the light is monochromatic.
6. It is good for tunnel lighting as the elongated lamps may be aligned end-to-end to produce a continuous line of light, eliminating any stroboscopic effect.
7. The SOX lamp can be operated on low-cost electrical control gear.
8. SOX lamps do not require a cooling-down time before they switch back on.
9. They are easier to service than other lamp types.
10. Yellow is a cheerful colour of light and can help to combat the winter blues.
11. It can be disposed of without concern for some of the toxic materials found in some types of lamp such as mercury.

How to buy

Buying new: GEO-Technik, based in Germany, supply new 35W SOX streetlights. The following two models are available:

GEO-Technik Alto SOX 35W lanternGEO-Technik Alto Kelvin 35W

GEO-Technik also sell some spare parts such as lamp tubes (sizes of 35W and 90W are certainly available) and ballasts. Alternatively, SOX spare parts can be sourced from eBay and elsewhere on the Internet.

Buying second-hand: Here are a few suggestions ...

1. A council who is taking SOX lamps out of service may be willing to pass them on, subject to their discretion. This option is more likely to be applicable in the UK or in other areas where SOX/LPS exists.
2. SOX streetlight enthusiasts are often willing to sell, buy or exchange lanterns. Many of them have their own websites. In the UK there is an Association of Streetlighting Enthusiasts (UKASTLE) - their website is
3. Ebay often has lanterns, lamp tubes and some other accessories for sale.


'Why Is He Interested In Streetlighting?' book

Soxtown - SOX streetlights simulatorFinally, below are a few links to other websites ... (Claire Pendrous) (Martyn Hicks) (Simon Cornwell) (French-language site)

All content on this website © Matthew Eagles 2005-2020 unless otherwise specified. Last updated 23 May 2020.

Your views

I would very much welcome your views on any aspect of SOX streetlighting, so please feel free to contact me. Please use the 'Contact' link in the navigation bar, or click here.