This part of IEC 61992 specifies requirements for d.c. disconnectors, switch-disconnectors and
earthing switches for use in outdoor fixed installations of traction systems.
NOTE 1 EN 50121-5 specifies requirements for electromagnetic compatibility (EMC).
NOTE 2 In this standard the word "unit" means "switch-disconnector and/or disconnector and/or earthing switch"
as defined in 3.1.5, 3.1.6 and 3.1.7 of IEC 61992-1.