Monday, 2 October 2017


TYPES OF FORWARD SIGNAL
1.On- hook signal
2.Off- hook signal
3.Pulse dialing
4,Push Button/DTMF

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TYPES OF BACKWARD SIGNAL 1. Dial Tone 2.Ringing Signal 3.Ringing Tone or Ring back Tone 4.Busy Tone signal 5. Number Unobtainable tone.