... cost effective and standards-complaint VoIP Media Trunk Gateway, which is generally called TG/SG or VoIP ... Voice Gateway, designed for enterprise users and ITSP (Internet Telephony ... PSTN and IP network, providing signaling transform between SS7, ISDN PRI, V5.2 signaling and SIP Protocol, as ... this model:Diagramm of its application: 2 E1 ISDN PRI SIP Gateway NC-MG900