One of the few features lacking from the LEGO Mindstorms system is an accurate positional drive. This has prompted the author to develop this interface circuit, which can control up to three servos of the type used in radio-controlled models via the IR-interface of the RCX brick.The three different types of LEGO Technic 9 V motors are more than adequate for most robotics projects. However, when accurate angular positioning is required, one can quickly become frustrated by the amount of play in the gears and start looking for a better solution. The servos used in radio-controlled models offer more precision. Of course, we will not only have to deal with mechanical interface problems of joining to other LEGO bricks: we will also have to operate under control of the RCX, which is a little trickier. The RCX brick is the main control element in the LEGO Mindstorms system. It consists of a microcontroller built into a large, bright yellow, LEGO brick.