5 points on class lecture 3 ->

1: I learned about the Automatic switching system which doesn't need any human handling.

2: automatic switching system is of two types  : electromechanical ,                              electronic

Electromechanical consists of  : space division switching and time division switching 

Electronics switching system consists of step by step system and  crossbar system.

3: space division switching is used in stronger and crossbar system

4: in time division switching sample values of speech signals are transfered at fixed intervals 

5: time division digital switch can be designed by using a combination of space and time switching techniques