The 3SB3000-4QD01 is a Siemens safety relay unit designed for use in monitoring safety circuits. It features four safety inputs, each with built-in diagnostics and is suitable for monitoring emergency stop circuits, two-hand operation switch systems, guard interlock switches, and other protective systems in accordance with EN/IEC 60947-5-1. It includes an LED display to indicate the status of the system, and has two potential-free changeover contacts for connecting other external devices. The 3SB3000-4QD01 is certified for use in industrial control systems and is certified for use in UL/cUL, CE and RoHS applications.