to add, in my point 2, i was told by the PABX vendor that i need a DISA card in PABX to connect the calls from the remote site to the local extension because the cisco FXS can not send digit to the PABX and PABX therefore need a auto-attendant card (DISA) so that the remote user dial the extension when promted by the DISA for extsion number. It’s Like a 2-step dialling.