The ESP-125 is a traditional 120V control that incorporates a current sensing circuit that automatically lights a quartz lamp when the main HID lamp is extinguished. For use with HPS or Metal Halide (probe-start or pulse start) magnetic ballasts with a 120V tap or input. 50/60 Hz Operation. Compact and simple to wire. Operates on HID circuits from 39-1500 watts. Operates auxiliary lamps up to 500W. Patent Pending.