In automation and closed-loop control, working with analog signals is unavoidable. Interfaces of 0 to 10 V and 0/4 to 20 mA have become established in this field. Interface converters load the coupling function for analog signals on the input side as well as on the output side. They are indispensible. where analog values are processed with electronic controls. In the harsh industrial environment, signals often have to be transferred over large distances. Electrical isolation is necessary due to the various different power supplies. Potential differences and losses due to cable resistance must be. prevented. Electromagnetic disturbances and overvoltages can affect the signals especially at the input end and even destroy the analog modules. With regard to the output, short-circuit protection is of particular importance. The devices are EMC-tested acc. to EN 50081 (emission). and EN 61000-6-2 (immunity). The analog signals correspond to IEC 60 381-1/2.