Open filterClose filter input output power-supply interface / protocols display / operation design DIN rail mounting Screw terminals device functions Overvoltage protection Reset filter Overvoltage Protection Image Article Description Input Output Auxiliary voltage Designs AD-BS 1 ST Surge protection for signal lines - Rough protection without series current limitation 2 wires 2 wires and protective earth - ST AD-BS 2 ST Surge protection for signal lines - Rough and fine protection without series current limitation by resistors 2 wires 2 wires and protective earth - ST AD-BS 3 ST Surge protection for signal lines - Rough and fine protection with cross-voltage limiting and longitudinal current limiting by resistors 2 wires 2 wires and protective earth - ST