The DB-24R consists of 24 form C, electromechanical relays for efficient switching of load by programmed control . The contact of each relay can control a 0.5 A /110 V load or 1A / 24VDC . The relay is energized by applying a 5 voltage signal to the appropriate relay channel on the 50-pin Opto-22 compatible connector or D-Sub 37 connector . Twenty-four enunciator LEDs, one for each relay, light when their associated relay is activated . To avoid overloading your PC’s power supply, this board needs a +12VDC or +24VDC external power supply.