Detects current drawn by a locomotive or lighted piece of rolling stock. Unpowered equipment can be detected by using metal wheelsets with resistors connected across the insulator. Will directly drive 2-color lamp r LED-type block signals. 250 ma. output (500 ma. for BD-2HD). Circuit boards are designed for easy daisy-chain wiring of multiple blocks and will snap into a section of Printed Circuit Mounting Track. Requires 10-18V DC. Works in any scale and with most track power, systems including most forms of carrier control. 3 amp capacity.