Developers of switched-mode power supplies face the challenge of developing their circuit to be EMC-compliant. Conducted interference particularly occurs in the input circuit whereby other electrical equipment can be disrupted. Therefore the conducted interferences are first checked at the beginning of an EMC test of power supplies. The developer can already perform measurements accompanying the development during the development phase to obtain an impression of possible interference. This Application Note describes the procedure for examining differential mode interference in the input circuit of DC/DC switching regulators.