2D & Double Ds
The 2D or Double D was originally a fluorescent lamp, and part of the CFL family except that its tubular design is unravelled into a large, flat, twin-d shape for the purpose of fitting into low-profile luminaires. First introduced in the 1980s, the 2D lamp is readily available in dimmable or non-dimmable forms, and uses either a 2-pin or 4-pin connection.
For a greater initial outlay, LED 2D lamps can be bought. These typically offer over 50% in energy savings against the fluorescent originals, and also boast twice the lifespan. Other advantages over fluorescent equivalents include: immediate full power (CFLs require a warm-up time); no fragile glass to break; shock proof and vibration proof; no mercury, making end-of-life disposal easier; and extremely reliable low-temperature performance.
Some LED versions of the 2D also include a microwave motion sensor, which is made possible by the ability of this sensor to operate through luminaire diffusers and lenses. PIR sensors do not possess this ability, since their passive detection of changes in IR radiation require an unobstructed view.
Investment in LED usually has an extremely fast payback with incandescent or halogen light sources, but the battle is a little more hard-fought against fluorescent. The latter has the advantage of cheap up-front cost, but LEDs are particularly well-suited to outdoor environments and will still likely halve running expenses. This obviously has more significance in a light that is kept on for long durations.
Double-D (2D) lamps are usually used in low-profile luminaires such as bulkheads, either indoors or out. They are the light source in a wide variety of environments, including car parks, warehouses, corridors, storage facilities, rear-of-house staff areas in hotels and restaurants, offices, and workshops.
GR10q (4-pin); GR8 (2-pin)