This part of EN 50123 specifies requirements for d.c. disconnectors, switch-disconnectors and earthing switches for use in indoor fixed installations of traction systems. NOTE 1 Switchgear assemblies, electromagnetic compatibility (EMC) and dependability are not covered in this part of EN 50123, but rather by other parts of this standard or other documents as indicated in EN 50123-1. NOTE 2 In this standard the word "unit" means "disconnector and/or switch-disconnector and/or earthing switch" as defined in 3.1.4, 3.1.5 and 3.1.6 of EN 50123-1. NOTE 3 Disconnectors, switch-disconnectors and earthing switches may have electrically latched mechanisms and, in such cases, may be indicated with the current term of "power contactors".