We have 30 Branches, in HO we have one 2811 Router with 4 FXS & FXO. FXO is connected to the PBX (1..) & FXS is connected to FAX. this router is acting as the gatekeeper for other branch Routers. When I call on the FXS Port it rings & I can speak but when I call on the PBX Extension it gives a busy tone. If somebody has GK/GW Scenario in one router pl help.