At 07:58 PM 2/7/99 -0300, Javier wrote:
>Thanks to everybody for answering, but I don4t want to detect or calculate
>the time a telephone is off hook, I want to know the time I4m conversating
>(how much is the company billing me !!!) It4s not that easy, is it??
>Thanks in advance
>Javier


Some old systems reverse polarity on connect, which you can detect with the
dual-opto current sensor, but most do not. Still, you could get a fair
sanity-check on them, if they report more time than you do (measuring loop
current) then you know they are wrong!