Protection against electric shock is provided by basic insulation only. Sales of these items have been banned since 1975 and they should not be used in an industrial, commercial or domestic environment.

Class 01 have at least basic insulation around live parts for protection, they also have an earthing terminal on the appliance but only two core power supply cords without an earth protective conductor. They should not be used in an industrial, commercial or domestic environment.

Protection against electric shock is provided by a single basic layer of insulation around live parts and any also any exposed metal or conductive parts that can be come live if a first fault developed should be connected to to earth. There is no symbol for a Class I product so if no symbol can be found assume that the appliance is Class I.

Protection against electric shock on Class II Double insulated equipment is provided by either two layers of insulation (basic and supplementary) around live parts or a material called substantially reinforced insulation. There should be no earth protective conductor on a Class II appliance. Class II appliances are identified with a box within a box symbol.

Also known a SELV (Safety Extra Low Voltage) Appliances are supplied with a low voltage (less than 50V) and are supplied via a safety isolating transformer.

All products / appliances fall into one of the construction classes above. The PAT Testing procedure varies for different construction classes.

Or CSA in cables is measured in mm2 and is used along with the length of the cable to calculate the resistance of a cable at a given temperature. The larger the CSA the more amps can be carried down the cable.