Class I – Earthed equipment. Fuses are also present so that if there is a short-circuit making the equipment “live”, current will pass to earth causing the fuse to blow.
Class II – Double-insulated equipment (not earthed)
Class III - Safety extra low voltage (SELV <24 volts AC)
Type B – Class I, II or III. Low leakage current 0.5 mA Class I and 0.1 mA class II
Type BF – Similar to type B but safer because patient is isolated
Type CF – Lower current leakage, 0.05 mA for class I and 0.01 mA for class II, protects against microshock