I now have an OpenVox A400P and it is working well. Thanks to Ade
Vickers for the recommendation, which I second.
However, I need to make a slow transition between a conventional
multiple-extension setup and a full VoIP network on these premises. So
at the moment the Asterisk box shares the PSTN connection with several
conventional analogue handsets.
The desired result for an incoming call is that the Asterisk server will
wait N seconds before answering (which I can arrange easily enough), and
if the call has been answered on one of the handsets by that time the
Asterisk server should ignore it completely. Otherwise it should start
checking CLID, prompting for extensions, and other good stuff, which
again I know how to do.
What is a good approach to making sure the Asterisk server doesn’t pick
up a call that has been answered elsewhere? (Ideally in pure dialplan,
but a perl AGI would also do.)