Functional Safety is the part of the overall system safety which depends on the correct functioning of safety-related systems for risk reduction. The intended functions of these systems, i.e. the safety functions, must be executed under defined fault conditions with a defined high probability. For the first time, a standard, the relevant generic standard IEC 61508, demands a quantitative proof for the residual risk! The standards IEC 61511 (Process Industry), IEC 61513 (Nuclear Power Plants) or ...