[Asterisk-Users] Linking asterisk to an existing small office PBX

[Nick Burch]

Hi All

I've done some reading on the wiki and read some of the mailing list 
archives, but can't see anything on this. I guess this means I'm either 
searching on the wrong thing, or have totally the wrong idea... Can anyone 
suggest if the following is possible?


Currently, our office has a 24 analogue extension PBX, and 2 ISDN lines
providing it with external connectivity. We have several analogue
extensions spare, but no capacity to add fancier connectors to link to an
asterisk system (as most of the PBX linking guides detail). All our phones
are bog standard analogue ones.

We'd like to use an asterisk system to allow some calls to be routed out 
via a VoIP gateway. We'd also like to allow some inbound SIP calls to be 
handed to the PBX.


I was considering building an asterisk system, and adding a few FXS cards
to it. I'd plug these into the spare analogue extensions on the PBX (is it
FXS, and not FXO I'd need when connecting to a PBX?) If people wanted to
make a call using a VoIP gateway, they'd dial one of the asterisk
extensions. They would then be connected to the asterisk box by the PBX,
and could dial the real number they wanted. Finally, asterisk would
connect them to an external SIP gateway, which would do something useful
with the call.

Additionally, I'd like people working from home to be able to connect via 
SIP to the asterisk box, and then have their calls routed to the PBX down 
an analogue line.


Is this possible, and is it even a desirable setup?

Thanks
Nick