Hi Shahzad,

You get at the IRQ the exact frequency in the line (provided within the bandwidth) during the CallProgress mode, but at the IRQ it is only in Square Wave form (digital form which is good for you)

Now imagine that B party only goes off hook and does not speak anything at all.......

So in this case how would you know "normally" that B party has picked the handset ??

Obiously by hearing the tone (cadence). When stop hearing the ring tones you "believe" that call has been answered.

So you got to program the chip in a way that it could listen the "tone" from the IRQ pin.

in other words program the chip in a way that it could detect some frequency at the IRQ pin .

When bell is ringing at the B end then your IRQ pin is at one of the two following states:

1. frequency when you hear tone
2. DC when there is silence

So you can program your chip to measure the length the tone length and silence length. You can compare these lenghts with standards and decide that the ring is going to B party.

whenever there is a difference between the current measured lengths and the standard, then "believe" that B party has picked to answere. "SIMPLE, isn't it :-)"

Before you start measuring the tone lengths you got to "determine" whether is ring or BUSY.

Its very easy:

take first couple of tones and measure with standards of Busy and Ring, then decide what is the case.

see, "ITS DAMN EASY, I have done it"


My side (-:-( Your side

To be on my side, you got to undestand me...


Babar