The AQY210KSX is a small-form-factor PhotoMOS relay featuring integrated short circuit protection in a latch-type configuration. It operates with a load voltage rating of 350V AC/DC and a continuous load current of 120mA, housed in a miniature SOP4-pin package. The device incorporates an LED input stage with typical operate current of 1.1mA and turn-off current of 0.3mA, delivering fast switching performance with typical turn-on time of 0.7ms and turn-off time of 0.07ms. When output current exceeds a fixed threshold (typically 200mA), the short circuit protection activates within 50µs, cutting off load current and maintaining the off state until the input is cycled. The relay features low on-resistance of 23.5O (typical) and minimal off-state leakage current of 1µA maximum, with I/O isolation of 1,500V AC. Common applications include modem and telephone equipment, measuring and testing equipment, security systems, and industrial control circuits where reliable switching and overcurrent protection are essential.