The FK4XX Series is a rich source of projects for classroom construction and are ideal demonstrations of applied sensors of several types. Most of the FK4XX series embody three of the basic elements of electronic control i.e. Input, Process and Output, in broad range of economical, easy-to-build circuits. An additional benefit of this series is that these proven, functional control units are easily adapted to industrial, security and domestic systems. These units are available also as pre-assemblies under the FA prefix.