Functional insulation: Insulation between conductive parts which is necessary only for the proper functioning of the equipment. Functional insulation passes a signal or power from a system at one voltage potential to another system and a different voltage. Functional insulation does not protect against electrical shock..

Basic insulation: Insulation applied to live parts to provide basic protection of persons against electric shock.

Double insulation: Double isolation takes a system with basic insulation and adds a supplementary insulation layer between the electrical parts and the end user to reduce the likelihood of electrical shock in the event that basic isolation fails.

Reinforced insulation: A single insulation system applied to live-parts, which provides a degree of protection against electric shock equivalent to double insulation. A device with reinforced isolation provides basic isolation; plus, the insulation is designed to provide the physical separation between printed circuit board traces, cores, windings, pins, and so forth.