Hi Shahzad,

More you ask more you would only get confused without first "ACTUALLY" making something. Other things 2wire ---> to 4wire you don't need.


How to go OFF / ON hook:

The transformer that I mentioned in previous postings is used to go Offhook when connected to Line in parallel. to go Onhook just disconnect the transformer. A relay can be used to connect the transformer.

How to detect the Ring Signal:

Make a rectifier bridge. connect one wire of the line (say tip) to one AC point to the bridge. Connect the other wire of the line (say ring) to the other AC point of the bridge but thru a .33uF / 400v Capacitor. Use the DC side (out put of the bridge) to energize the input of an opto isolator (say 4N35).

When there is a ring signal in the line (60 or 90 V ac) then the opto would give you an -ive pulse out.......

Use this out put from opto to detect the ring incoming. Then latch the relay to go OFF hook to answer the call on the incoming ring.

Purpose of 8880:

This chip "IS NOT DESIGNED TO DETECT RING SIGNAL"

Just connect 8880 to the line (single input or differential input configuration) directly to the line. It will only out put DTMF to the line or detect the DTMF coming from the line in transceive mode. It will only detect tones in the line when in call progress mode.


You send and receive the DTMF you first got to go OFF hook.


I have been reading your postings on this issue persistantly.

You have not yet understood the data sheet of 8880. You also have not gone thru the sites at <epanorama.net> that I asked you to see.

INSTEAD, you seem to prefer to keep asking and listening to gurus (not me) with their high tech propositions which only makes you more confused cuz you haven't understood the basics on telephone yet......

My sincere advice to you would be:

Stop asking any more. Do some practical work as I told you. You can ask me if you have any problem (practical)

After you have implemented the basic DTMF tranceiver and call progress monitor, then you can go ahead with high tech telco goodies. Then I would like to learn from you.

Kindly do take care of time of everybody on this forum.

We all love to teach you swimming, but kindly HELP us and at least step in the "POOL".


Best of regards and good luck.

Babar


PS: you will get all the schematics on the net once you search on empanoram.