wrote:
Many thanks, I'll have a bash when I get a free hour or three. That
gets slotted into extensions.conf or extensions_custom.conf I suppose?

extensions.conf. You'll need some kind of framework around it. I'm
assuming you have some kind of phone connected to the PBX, which you'll have
to arrange to land in that dialling context:

[fred]
....the lines I listed before
exten = h,1,HangUp

The last line above hangs up the PBX phone when the SIP call has hungup.
Let's assume there's a SIP desktop phone which connects to your Asterisk
server, the details of the connection will be described in sip.conf and will
have a line:
context=fred
which means that when someone picks up the desktop phone any dialling will
be passed to the [fred] block above. This tutorial should give you an
idea:
http://www.asteriskguru.com/tutorial...p_ipphone.html

The same goes for softphones, IAX phones or PSTN phones via a linecard.

Would that interfere with/bypass FreePbx's Outbound Routes? If for
some reason Betamax was down, then a second trunk (another SIP
provider or landline) would be used.

Perhaps someone who knows FreePBX can comment? It might help to have a look
at what underlying Asterisk rules it generates.

Theo