The R. STAHL 9170/20-10-21 is a high-integrity, single-channel switching repeater designed for the intrinsically safe operation of NAMUR sensors, optocouplers, and mechanical contacts located in hazardous areas. This device provides reliable 3-way galvanic isolation between the input, output, and auxiliary power circuits, ensuring signal integrity and system safety. It features a relay output with a change-over contact and incorporates line fault detection (LFD) for short-circuits and wire breaks, with an LED indicator for diagnostics. The operating mode (N/O or N/C) and LFD can be easily configured via DIP switches, making it a versatile solution for process automation and control systems in explosive atmospheres.