||Osglim Neon Discharge lamps have been manufactured in three different styles - a lighting lamp, a series of small indicator lamps, and also letter lamps (as pictured here).
The 5-watt Letter lamps employ one large electrode stamped out from sheet iron, in the shape of a letter or number. The second electrode is simply a small iron wire extending from the stem behind the centre of the main electrode. Lead wires are sleeved in short pieces of glass tube to interrupt the glow discharge in these regions. Swedish iron is the preferred electrode material for these lamps on account of its low rate of sputtering and ease of outgassing by bringing it to red heat during the pumping stage. When arranged side by side, illuminated signs could be created for shop windows etc.
Lighting lamps are of a similar construction, however the form of the electrodes is optimised to generate light as efficiently as possible, and ensure uniform distribution around the lamp. They used to be popular as nightlights. The half-watt Indicator lamps are in small pygmy or tubular glass bulbs and generally have electrodes formed from sheet metal, either as a split disc, or a disc with an annular ring.
All lamps incorporate a ballast resistance inside the cap and are filled with a neon-argon penning mixture for easy ignition on the mains electricity supply. Incidentally the name "Osglim" is frequently found on pre-1950's neon lamps from the GEC. In the same way that the Osram brand was used for general lamps and the Robertson brand for carbon filament lamps, Osglim was another GEC trade name used exclusively for neon glow lamps.