Equipment: Lamps and Gear

Abstract

Since 1932, the low-pressure sodium lamp, the first commercially-used gas-discharge lamp, has bathed many roads in its yellowish light. Within a few years it was joined by the high-pressure mercury lamp providing bluish-white light. The high-pressure sodium lamp, introduced in the late 1960s, with its yellow-white colour and much higher efficacy, then relatively-quickly replaced the high-pressure mercury lamps in a large number of applications. There, where lighting levels were not high and white light was preferred, fluorescent lamps, usually of the compact type, were sometimes also employed.

In the last part of the last century induction lamps with extremely long lifetimes were introduced. Around the same time, metal halide lamps with their high-quality white light became available with lifetimes long enough for them to be employed for road lighting—high lighting-level road lighting with high quality white light of high efficacy had become a possibility.

The beginning of this century marked the commercial introduction of a fundamentally new type of light source, made of solid-state semiconductor material: the light-emitting diode, or LED. Today, LEDs have taken over from many gas-discharge lamps used in road lighting. The principle of operation, the construction and the application possibilities of all these light sources are widely different and will be described in this chapter, as will the auxiliary electrical devices, such as ballasts, igniters and drivers, needed for their proper functioning. Because of their importance today, extra attention is given to LED light sources.