The CM-MSS.21S belongs to the CM-MSS thermistor motor protection relay range. It operates with a rated control supply voltage of 24 - 240 V AC / DC and has a 1 n/c + 1 n/o (SPDT) output with contacts rated at 250 V / 4 A. It features one sensor circuit to monitor PTC temperature sensors and works according to the closed-circuit principle. The sensor circuit of the CM-MSS.21S is short-circuit, as well as interrupted-wire monitored and the relay will be reset automatically after the failure has been removed. This protection relay is certified according to the ATEX directive 49/9/EC. 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.