Separation of busbars from the functional units and separation of all functional units from one another, including the terminals fro external conductors which are an integral part of the functional unit.

Protection against contact with live parts and limitations of the faults between each of the functional units ( propagation of electrical arcs, etc.)

TWO TYPES OF FORM 4 SEPARATION AS SPECIFIED BY I.S. EN 60439-1

FORM 4A:

Terminals for external conductors in the same compartment as the associated functional unit.

FORM 4B:

Terminals for external conductors not in the same compartment as the associated functional unit, but in protected spaces or separate closed compartments.