Capsules are small bulbs normally used wherever space is at a premium. They are identified by the distance between the centres of their two pins, expressed in millimetres. For instance: a G4 capsule has a 4mm distance from pin centre to centre.
Though they are named by their cap size, capsule types are often described in Europe by LIF codes. These are assigned by the Lighting Industry Federation of London, and are used in sub-dividing capsules and other lamp types into groups according to their primary application. For example, an ‘A1’ prefix indicates a capsule for slide projectors or overhead projectors, whilst a ‘T’ prefix refers to a bulb intended for theatre use.
A 3-letter code may also be seen on some capsule models, which is the American ANSI code used to describe bulbs. For instance, an ‘EHJ’ suffix denotes a 250W 24V G6.35 capsule with an average rated life of 50 hours.
Common amongst halogen capsules and dichroic reflectors are ‘M’ class display lamps, which are suffixed by a number or combination of numbers and letters. For example, an M47 is a 12V 20W lamp with a G4 base and an average rated lifespan of 2,000 hours.
Capsules can be dimmable or non-dimmable, and are available across a wide choice of technologies, including halogen, energy-saving halogen, CFL, HID, and LED. As usual, LEDs offer enormous energy savings over halogen equivalents, and are readily available in popular G4 and G9 low-voltage and mains-powered capsules. Countering this, halogen is fantastic for colour, with its reliable ‘continuous spectrum’ output and crisp bright light. HID lamps offer an excellent combination of energy-efficiency and long lifespan for specialist commercial applications.
Most of these capsules are used in compact light fittings and housings in applications such as desk lamps, ovens, caravans, boats, cabinets, wardrobes, small downlights, projectors, medical equipment, theatre, and shop window displays. The bigger HID tubes and capsules are often used in powerful retail display applications and downlights.
G4; G6.35; G8.5; G9; GX6.35; GY6.35; GY9.5; PG12.1