An electric leakage preventive apparatus comprises an equivalent impedance which is equivalent to a load leakage impedance of a load in a main body; a switching unit for applying voltage to the equivalent impedance; a driving unit for driving the switching unit; and a control unit for generating...http://www.google.com.hk/patents/US5748459?utm_source=gb-gplus-share專利 US5748459 - Electric leakage current prevention using an equivalent impedance
