The CM-SRS.21S is a single-functional current monitoring relay from the CM single-phase monitors range. This monitoring relay operates with a rated control supply voltage of 220 - 240 V AC and has a 2 c/o (SPDT) output with contacts rated at 250 V / 4 A. It provides a RMS measuring principle for DC and AC currents with 3 measuring ranges: 3-30 mA, 10-100 mA and 0.1-1 A and works according to the open-circuit principle. The CM-SRS.21S is configurable for over- or undercurrent monitoring. The hysteresis is adjustable within a range of 3 to 30 % of the threshold value and the tripping delay is adjustable over a range of instantaneous to 30 s (0, 0.1-30 s). A sealable transparent cover for protection against unauthorized changes is available as accessory. The device offers screw connection technology with double-chamber cage connection terminals.