Signalling Tones

1. Dial Tone : Indicates that exchange is ready to accept the dialed digits  from subscriber.
2. Ringing Tone  :- The tone send to called party after establishing the call.
3. Busy Tone:-A bursty 400  Hertz signal to inform  the calling party that subscriber is busy.
4. Number unobtainable tone  :- Called party line is out of order
5. Call in Progress tone(Routing tone ):-When a call progress through no. of exchanges subscriber listens a number of tone due to different exchanges involved in the call routing.