telephone call counting unit

[rahila]

Hi,
Im a B.Tech student and now im in tension of my projects.. I would like to design a call counting unit that can be connected to the telephones., the call counter should count all out going cals only and incoming calls should not be counted.. can any one help me to find a method to track the instant at which the called party attends the call so that i need to start counting at that instant.. please help me to solve this.

 

[RMMM]

Monitor the line voltage.

The line voltage changes during a connected call, or phone ringing. I no longer have a land-line so I cant help there, but you can fine telco line voltages with google.

Using a comparator, you can trigger a counter when the line hits the "connected-call" voltage.

 

[rahila]

thank you..

 

[rahila]

can you help me to know what all datas will be available at the data pin out of the telephone?

 

[RMMM]

I dont understand what you mean.

What data pin?

Are you talking about a cell phone or land-line?

 

[crutschow]

Monitor the line voltage.

The line voltage changes during a connected call, or phone ringing. I no longer have a land-line so I cant help there, but you can fine telco line voltages with google.

Using a comparator, you can trigger a counter when the line hits the "connected-call" voltage.

That will count all calls. The OP wants to count only outgoing calls, which requires additional circuitry.

One way is to detect the ring voltage and use that to cancel the count if the phone is answered shortly after a detected ring. The ring could trigger a retriggerable one-shot delay that would inhibit the count for a several seconds after each ring (delay longer than the normal interval between rings).

 

[KMoffett]

Here is a bit of a circuit (modified a little) that I made many years ago to add a Hold function to an old standard home multi-phone circuit. Perhaps the outputs can be used to implement Carl's concept.

Ken

 

[rahila]

I dont understand what you mean.

What data pin?

Are you talking about a cell phone or land-line?

Actually i meant land-line.

 

[rahila]

do you men that i should go for programming?
can you please provide me with the circuit that you meant?

 

[KMoffett]

Who or what post are you asking about?

Ken