What is a VoIP gateway?
A VoIP gateway is a network device that converts voice and fax calls, in real time, between the public switched telephone network (PSTN) and an IP network. The primary functions of a VoIP gateway include voice and fax compression/decompression, packetization, call routing, and control signaling.
Gateways provide IP connectivity to legacy PBX equipment, and PSTN connectivity to IP PBX systems.