1). Automatic switching system can be divided into two parts. They are :1.Electromechanical and 2.Electronic.

2). Electromechanical switching system can be divided into two parts:1.Step - by - step  and 2.Crossbar

3).In space Division switching system, dedicated and exclusive switching path should be established.

4).In electronic switching system, we use control function and logic.That's why information are stored. Then that stored information are provided & information can be send.It's called Stored Program Control(SPC).

5). In time Division switching system, we Don't need any dedicated  path.Here the same switching path may be shared by more than one subscriber pair.By using any node we can send data.