The GMRT servo system is a dual drive position feed-back control system. It can track a source in the sky with an rms accuracy of . To realise such a system practically, the expertise from various engineering disciplines are put to work. In order to understand such a system, one has to become familiar with the theory of feedback control systems as well as its application for position control. This chapter discusses these issues. The material is presented in an simplified form and an effort has been made to use, wherever possible, graphical explanations instead of a mathematical treatment.