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The main part of the paper is dedicated to a new philosophy of protection against electric shock. Triple safety is postulated consisting of three safety measures to be taken in electrical installations. The first line of defence is always basic insulation as means to avoid the risk of touching a live part (Basic protection). If this first line of defence is defeated in case of an insulation fault the second line of defence is built up as protection against indirect contact (fault protection). Advantages and disadvantages of bonding to the PEN-conductor, protective earthing and electrical separation are briefly discussed. Experience shows however that also this second line of defence may break down. Therefore a third line of defence, especially necessary for portable equipment i.e. for circuits with socket outlets, is proposed as an additional protection which in general consists of residual current-operated circuit-breakers with a rated operational residual current not exceeding 30 mA.