Version 1.0 RCX bricks feature a power adapter jack in addition to batteries. In version 2.0 (as well as later 1.0s included in the RIS 1.5), the power adapter jack was removed. Power adapter-equipped RCX bricks were popular for stationary robotics projects (such as robot arms) or for controlling Lego model trains. In the latter context, the RCX might be programmed with Digital Command Control (DCC) software to operate multiple wired trains.
