[Lucien Nunes]

Here's an unusual lamp on an unusual cap. These were made for the illuminated stops on some Compton organ consoles in the 1930s-1960s, and pushbuttons on certain Compton-derived Strand lighting controls such as System C. These were in effect large illuminated momentary pushbuttons about an inch in diameter, with the subtlety of being double-touch (a second contact closes if pressed with extra force).

The lamp has a flattened envelope with a coiled filament forming a supported arc facing the front. The cap consists of a plain sleeve contact with a very long rigid wire emerging from the insulator forming the second contact. This locates in a small hole in the back of the switch body. The lamp does not move when the button is depressed.

The filament is under-run for long life and vibration-resistance and is as much a heater as a light - it dissipates a good fraction of a watt at 18V while giving out the colour seen in the attached pic. This example was borrowed from the 1937 Southampton Guildhall organ and is probably original. We will soon be changing them to LED not because there is anything wrong with the lamps, but to minimise the exposure of the plastic parts to heat as they are starting to deteriorate. On some heavily-used organs, the more popular stops are badly discoloured and damaged.