[Asterisk-Users] PBX <-> AST <-> AST <-> PBX

[Ezequiel Golub]

Im trying to come up with a cost effective way to unite two PBX using VOIP.
My idea is that since most companys here (Argentina) are not ready cough up
the money to go to full-fledged VOIP, they might be willing to pay for a
hybrid-solution: a kind of "point-to-point" line using VOIP, which let's
them dial an extension on the other PBX.


What i want to accomplish:
---------------------------
User dials a number on his analog phone connected to a standard PBX, he is
greeted with a message:
"Which branch office do you want to connect to? (offers options)"
User chooses a branch office, hears:
"Enter remote extension"
User talks to that extension.

How i want to accomplish that:
------------------------------
One asterisk box attached to each PBX (will be called AB from now on).
ABs should have a 4 ports FXS  card connected to specific ports on the PBX
and a broadband connection.
The PBX should have a workgroup configured to dial in the first free
extension on the AB.
If AB receives a call, it routes it to the correct remote AB, which should
be able to pick up the first available FXS port to dial in an extension.
(here is where i get confused, i need 4 FXS ports and 4 FXO ports for that ?
or with just FXS im fine?)

What i want to know if this is basically a doable idea, because if it is i
can think about investing the money and time to put up a demo of it and try
to sell it. What i dont to happen is that i invest about 1000u$s computer
and telephony hardware to find out what i want is IMPOSSIBLE.

Could someone please tell me that im not crazy or trying to reinvent the
wheel ?

Thanks a lot.

Ezequiel Golub.