Control system is very important in field of engineering as it finds wide application not only in engineering but also in non-engineering discipline. It makes control system very special and interesting. Study of automatic control system involves a lot of mathematical treatment. The first automatic control system is a fly ball governor to control speed of a steam engine. It was invented by James Watt in 1770. This governor used to keep the speed of the engine constant by regulating supply of steam to the engine. Control system also finds application in non-engineering fields. A simple example is an automatic anaesthetic control. The degree of anaesthesia of a patient undergoing operation can be measured from encephalograms. More complex and complete feedback models are now available in both engineering and non-engineering field. This make study of control system more popular and challenging. BASIC ELEMENTS OF CONTROL SYSTEM A control system consists of several elements where each eleme...