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.