The CM‑SRS.21S is a single‑phase current‑monitoring relay from ABB’s CM‑SRS series. It monitors AC and/or DC current and triggers an output when the measured current goes above or below a set threshold — providing either over‑current or under‑current protection. The device supports multiple measuring ranges for flexibility, and allows adjustment of hysteresis and tripping delay. Output is provided via dual changeover (SPDT) contacts, and the relay is designed for DIN‑rail mounting with standard screw‑type terminals.
