HI..


When a microcontroller dials a number on telephone .... then you get tones which needs to be analyze by the micrcontroller to decide the nature of the call progress.

Now here is what happn when some one dials a number you dail a number and when the other phone starts ringing you get tone
tttt-------tttt-------tttt--------tttt--------tttt---tttt---tttt----tttt


you can see the first portion of the ring contains a little longer delay as compared to the last portion... first portion indicates that the other phone is ringing ..... and after for example 15-20 bells the phone line give tone with short time to indicate the call has not been received....
simularley if you dial a number and if the other phone is busy then you get this tone

tttt---tttt---tttt---tttt---tttt

tones with short time delay around 1 second.... indicating that the other phone is busy.



other information is that when you get a tone tttt it means some frequnecy like 300Hz or some thing..


Now the Question....
1- Does different tone like Rining, busy or call not received has different frequencies.... or do they all has the same frequnecy ...

2- if all tones has the same frequency then that means microcontroller has to analyze the time between tones.. this is what am i doing and most of the time it works. and my algorithim decides whether the call is received or not...





Shahzad