Im working on this proyect, i have on one office a KX TDA200 pbx that has an kx-tda0484 (ip gw4e), i want to connect this voip trunk to an kx-T616 that is in another office, the offices are connected trough a VPN. The trouble is that the T616 doesnt work with voip cards, so ive researched several voip fxs gateways but they all seem to work with SIP, and i cant find where to configure SIP on the tda0484. Perhaps a firmware upgrade will allow this? or do i need a different gateway? thanks..