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 SELV system without provision for protective earthing (class III) and a rated current not exceeding 25 A per conductor, or – a combination of the 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 in different sector openings (mains or SELV).

IEC 60570 : 4.1