Hello! I have a question regarding VoIP Gateway y IP-BPX. I have installed a 3CX Phone System, but I have some doubts regarding the best type of e VoIP Gateway to connect to PSTN lines. I have 3 ISDN BRI cables that reach our office from the telephone company´s switch board. Each U-interface enters its NT1 (Network Termination). NT1 transforms U-interface into S/T-interface and connects to IP-BPX Nortel M6501-R. Do I hacve to use, for example, a "GrandStream GXW-4108 8-ports Analog FXO" VoIP Gateway and connect to IP-BPX Nortel? Or do I need to use, for example, a "Patton SN-4634 3-port ISDN/BRI" VoIP gateway and connect directly to a ISDN BRI U-interface? Thank you very much.