There are five types of insulation to shield live components with hazardous voltages from other components and circuits. Operational insulation does not provide any protection against electric shock. Basic insulation is applied to live parts to provide basic protection. Supplementary insulation is independent insulation applied to provide protection should the basic insulation fail. Double insulation comprises both basic insulation and supplementary insulation. Finally, reinforced insulation is a single insulation system applied to live parts to provide a degree of protection against electric shock equivalent to double insulation. For power supplies, the minimum insulation requirements are listed here.