This International Standard applies to the following track systems with two or more poles for the connection of luminaires to the electrical supply consisting of, either -- a system with a rated voltage not exceeding 440 V between poles (live conductors) with provision for earthing (class I) and a rated current not exceeding 16 A per conductor, or -- a SELV system with a rated voltage not exceeding 25 V without provision for earthing (class III) and a rated current not exceeding 25 A per conductor, or -- a combination of two systems mentioned above (mixed supply system) for the connection of both mains voltage luminaires (class I or II) and SELV supplied luminaires (class III) simultaneously, but different sector openings (mains or SELV). The track system may also provide for the mechanical support of the luminaires. It applies to track systems designed for ordinary interior use for mounting on, or flush with, or suspended from walls and ceilings. These track systems are not intended for locations where special conditions prevail as in ships, vehicles and the like and in hazardous locations, for example, where explosions are liable to occur.