Calls are sent as data packets over the computer data network instead of the traditional phone network. Phones share the network with computers so no separate phone wiring is required. With the use of a VoIP Provider, SIP Trunk, you can connect existing phone lines to the PortSIP PBX to make and receive phone calls via a regular PSTN line. You can also use a VoIP Provider, which removes the requirement for a gateway. PortSIP PBX interoperates with standard SIP softphones, IP phones or smartphones, and provides internal call switching.