in this lesson i learned a lot of new things as well as got to review some old ones.

1:  advantages of automatic switching system over manual switching system -->

  (a) manual switching system  need and operator to connect the call which leds to  different problems  , but in     automatic switching system we don't need an operator.

(b) A greater degree of privacy is obtained in automatic exchange .

  (c)Establishment and Release of calls are faster in automatic exchanges.

2:  there are 2 methods used for ROTARY DIAL TELEPHONE . which are -->

 (a) pulse dialing

(b)multifrequency dialing

3:  in pulse dialing system the number of pulses in a train id equal to the digit value  it represents except in the case of zero which is represented by 10 pulses .. so if ii press 4 , four pulses will generate to prodece the number  four .

 4:  Five subscriber related signalling functions which were  performed by the operator:

 1. Respond to the calling subscriber to obtain the identification of the called party.

2. Inform the calling subscriber that the call is being established.

3. Ring the bell of the called party.

4. Inform the calling subscriber, if the called party is busy.

5. Inform the calling subscriber, if the called party line is nobtainable for some reason.

5:  there are various signaling tones which has different frequency -->

  (a) dial tone  : 33 or 50 or 400hz continuous

  (b) ringing tone  : 400 or 133 hz tone

  (c)busy tone : 400 hz

  (d)number unobtainable tone : 400 hz continuous

 (e) call-in -progress : 400 or 800 hz