DIA53S72420AF is a small current monitoring relay designed for 1-phase AC over-current detection with a built-in current transformer and adjustable set-point. It features a 2-wire self-powered connection, input current range of 2–20 AAC at 50 Hz, and an integrated solid-state NPN-PNP open collector output with normally open contact rated for 100 mA maximum load current. The relay delivers fast reaction time of less than 50 ms (for signal variation from -20% to +20% of set value), operates over -20°C to +60°C, and is housed in a 17.5 mm wide DIN-rail enclosure (17.5 × 81 × 67.2 mm) with IP 20 protection. Its 12 mm hole for insulated current-carrying wire, knob-adjustable set-point, and LED indication for output status make it suitable for industrial current monitoring, motor protection, and circuit supervision applications where reliable over-current detection is essential.