Useful Information     Class I equipment   Class I equipment has parts with functional insulation only and with provision for grounding. Class I equipment contains a carefully grounded conductive case which is the first line of protection agains a hazardous shock. Class I equipment always uses a 3-wire, grounded power supply cord or cordset.       Class II equipment   Class I equipment is provided with double insulation and/or reinforced insulation throughout and has no provision for grounding. Class II equipment protects the user from accidental shock through the use of two independent insulation systems. These appliances are sometimes referred to as being double insulated. A 2-wire ungrounded plug is used in class II equipment.       Class III equipment   Class III appiances are designed for connection to extra low voltage circuits.       Clearance   Clearance is the shortest distance between two conductive surfaces.       Creepage   Creepage is the shortest distance between two conducting parts measured along the surface of the insulating material between them.       Harmonised cable   "HAR" cable meets the requirements of Harmonised Documents HD-21 or HD-22 and will carry one safety agency approval which is recognised by other European safety agencies       Power supply cord   A power supply cord is a means of transmitting energy from the mains supply to an electrica deice through a flexible electrical cable. A cord is permanently installed in the device being powered, as opposed to a cordset, which is detachable.       RFI   Radio frequency interference is a phenomenon that is generated in electrical equipment as a result od switch closures, and by motors, inductors and various other complex electrical circuits. RFI is conducted from the point of origination through cables, it may present performance problems for adjacent equipment.