During burst testing with the S21 sensor which is installed on the assembly, electical signals from the assembly are transformed into optical signals. The pulse rate counter of SGZ 21 detects these optical signals. Futhermore, the MS 02 magnetic field probe can measure burst magnetic fields on the assembly and can transform them into optical signals during the test. This measuring procedure is suitable for signal monitoring during the burst tests or before and after measurements for controlling the EMC steps. The SGZ 21 conforms to following standards: EN 50 081-1/-2 and EN 50 082-1/-2.