🚀 go-pugleaf

In article <wb8fozDw6tDt.BLF@netcom.com>,
David Lesher <wb8foz@netcom.com> wrote:
>Simon Watkins <simon_watkins@nt.com> writes:
>
>>barrett@opera.iinet.net.au (Barrett Communications) wrote:
>>>I am looking for means of determining if a person has picked answered a
>>>phone (normal analogue).  

   I assume you want to detect answer from a different calling telephone,
not by monitoring the called line....

>In the US, this is termed "supervision"...
>
>There is no reliable supervision back to the originating
>line, with one exception.
>
>In some locales, CPC [a momentary drop in loop current is
>offered up on disconnection. But depending on it is a bad idea.
>
>The exception is ISDN. It does provide full supervision.

   I think ISDN is ideal (and fast) for this application.  But there is
another standard method available ONLY on analog 2-wire lines.  The feature
is called "Answer Supervision - Line Side" by some TELCos; we called it
"Calling Line-Side Supervision" on the 5ESS-2000 switch.  The interface is
simple - Tip/Ring battery & ground are reversed when the called party goes
off-hook and reversed again when the called party goes on-hook.  The line
is restricted to virtually NO features, and may not be compatible with
some out-side plant equipment (pair-gain devices).  It's also unlikely
to be tariffed as a residential feature, and only available on selected
switches....

Al Varney - just my opinion