components (Figure 7.84), which typically produce a dielectric strength between the input and output of a few 100 V to 10 kV, are frequently installed to transmit signals in process technology systems in order to isolate the field side electrically from the process side. Thus their function is similar to that of transformers and they can primarily be installed to block low CM interferences. However, they cannot provide sufficient protection against arising CM and DM interferences when being affected by a lightning stroke (.10 kV) above their transmitter/receiver surge withstand capability.