[Asterisk-Users] PBX-VPN-SIP-Asterisk trouble

[artifex maximus]

Hi all!

I have the following setup:
Phone lines -> traditional PBX -> Welltech 3802
-> VPN ->
Asterisk -> Linksys PAP2/Welltech ATA-151 -> phone

There is 2 pieces of Welltech 3802 (2 port FXO) connected to 4 (2x2)
PBX extensions. Asterisk is a proxy here. Each device successfully
register itself. I tried the setup above with Linksys and Welltech
devices as well.

I setup Asterisk as a local PBX and phones can call each others on
Asterisk side and possible transfering calls. I setup Welltech 3802
with hotline mode so if someone call the public number from outside
the call transferred through VPN and phone rings in front of me.
Great. It's still possible transfer call within Asterisk side.
Excellent.

The problem comes when I want to call extension on PBX side or
transfer incoming call to the PBX side. I got the line sound when I
press flash, the caller hear the MOH and when I call extensions on PBX
side I got only busy tone.

How could I tell that Asterisk send back the flash&DTMF on the same
PBX extension where call comes from? I think this is important for PBX
to connect lines "inside" right. How could I route outcoming calls on
a port of Welltech 3802?

An example (because my grammar is hard to understand :-)

Call from outside
1, PBX rings on connected Welltech 3802 port
2, Welltech 3802 "picks up" the phone and transfer to the specified
hotline number
3, (packets going through the VPN)
4, Linksys got an INVITE from Welltech and starts ringing phone
5, I pickup the phone and talk

A (local extension):
6, I press flash and got a line tone
7, I enter the digits of local extension (4 digits)
8, Asterisk search in registered peers and found it
9, Asterisk connect to SIP device & phone rings there

B (external extension):
6, I press flash and got a line tone
7, I enter the digits of local extension (3 digits)
8, Asterisk send a flash and the entered digits back to PBX via the
Welltech 3802
9, PBX connect to the specified extension & phone rings there

My question is how could I tell to Asterisk send back flash and DTMF
to PBX on the active connection? I'm stand at the B/8 and don't know
what I do. I digging the internet in last 2 days but no solution.

bye,
Zsolt