EMERGENCY-STOP circuits are common safety measures in all laboratory equipment and industrial plants. The EMERGENCY-STOP modules used here must meet the most rigorous demands with regard to functional reliability. Benchmark is the degree of selfmonitoring. The Machine Directive 98/37/EC, valid from 31.2.1994, only specifies global safety standards. Details on how to implement individual safety demands are defined in standards, e.g. by the European Committee for Electrotechnical Standardization (CENELEC), which form the basis for international standards.