It is a call which is made over internet protocol (VoIP). For example,
one can call using Google Voice to other recipient located miles away. Such
call can also be international.
Portech MV-374 is a 4-channel VoIP-GSM gateway, which is responsible for converting GSM signal into VoIP (SIP) protocol. Used as a terminal server to route incoming calls from GSM network operators, VoIP communication, as well as a device for switching IP PBX, protocol-based SIP (RFC2543, RFC3261) with GSM. The device is compatible with IP PBX Asterisk, Elastix, Trixbox, Free PBX and registered on the SIP-server as a terminal device.