1)4 to 32 FXO/FXS; 2)1 or 2 E1; 3)With SIP protocol; 4)Signaling support: SS7, ISDN PRI, R2, Q.SIG, V5.2; ... and combination our rich experience in the telephony technology with providing E1, FXO, FXS interface.NC-AD300E PBX has its powerful signaling ... Fax pass through etc..Product specification:* Provide 32 port FXS or FXO,can be hardware configured with plug-in module base on customer requirement ...