Industrial process equipment has often been connected to controllers using RS232, RS423 or similar communication interfaces. These are unbalanced communication lines with low communication speeds up to 1 Mb/s that can only be used for relatively short distance communication due to their susceptibility to disturbance signals. CE testing using the combination wave/surge and ringwave impulses is required for products having this interface type. In special applications the damped oscillatory wave (DOW) will also be used.