Positive indication whenever a section of a layout is occupied by rolling stock. Contains all circuitry to power two-color block signals at each end of the protected block. Will give proper indications if a train leaves a block by backing out. No modifications to rolling stock needed. Completely bi-directional. No additional driver boards or relays are needed. 250 ma. output can power lamp or LED-type signals. Requires 6-20V DC input. Independent of track power. Compatible with radio or command control systems.