... connect billing systems for public phone use, to connect VoIP gateway torealize VoIP call termination, to connect alarm system for security purpose ... , etc. It is not a VOIP gateway, nora GSM+VOIP gateway, It is a GSM Fixed Wireless Terminal that ... extensions;2) It can connect with ordinary telephone set, PBX , VOIP Gateway, Billing meter etc. ;3) Dialing tone frequency:450hz;44 ...