Hi Javier
 there is a circuit in some older telephone systems (TIE of Trillium for
example) that is called a system message detail recorder SMDR generally
they are RS232 output and will log time in time out and number dialed some
will even record the number of rings before answered. If you could find one
of these you would have all you need
good luck


Wil Reeder
teachtech@bc.sympatico.ca
Vancouver,Canada 0x33
solar,wind,tide, TEG  renewable energy

----------
| From: Javier <grijalba@CVTCI.COM.AR>
| To: PICLIST@MITVMA.MIT.EDU
| Subject: Telephone use & time calculation
| Date: Friday, February 05, 1999 5:52 PM
|
| Does anybody know, how to build a circuit to detect how much time my
| brothers  used the phone and which number they dialed. I was thinking to
use
| DTMF with 8870 and a pic to calculate the time, but don4t know how to
| trigger the start of time calculation, is there any tone for that???
(start
| and stop of the conversation)
| Anything would help thanks
| Javier