Surge protection for measurement and control applications without signal function or display. The following signals are protected by binary signals (SL - balanced load): Switching signals with and without a common reference potential of 24V, 5V to 60V. Two-wire systems typically have a common reference potential for binary sensors, actuators, and indicators such as limit switches, push buttons, position sensors, light barriers, relays, solenoid valves, and signal lights. It features a pluggable surge protection for interruption-free and impedance-neutral plugging and unplugging. Testable with a V-TEST tester. Space-saving design for up to 4 binary signals. The version includes a ground-free PE connection to prevent leakage currents due to potential differences. Complies with construction standards IEC 62305 and IEC 61643-22 (D1, C1, C2, and C3). Integrated PE foot safely conducts up to 20 kA (8/20 μs) and 2.5 kA (10/350 μs) to the PE. Colored labeling of voltage levels allows for quick identification in the control cabinet. The safety function includes a coding element for different voltage levels.