Voip Gateway

A VoIP gateway is a gateway device that uses Internet Protocols to transmit and receive voice communications (VoIP). The general term is ambiguous and can mean many different things. There are many such devices. They are quickly becoming the most common type of voice phone service in many areas.
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. Additional features may include interfaces to external controllers, such as Gatekeepers or Softswitches, billing systems, and network management systems.
Using a gateway to connect a VoIP phone system to traditional phone lines makes sense in situations where SIP trunks are not available or where your application requires the reliability of the PSTN. It also makes it easy to build redundant systems. The gateway normally communicates with a primary IP PBX. In the event of a failure on the primary the gateway can communicate with a backup system.
Adding VoIP to a legacy PBX system is a great way to add features and reduce costs. The gateway connects to the legacy system through either analog or digital trunk ports. The PBX sees the gateway as either the phone company or as another networked PBX. Calls from the PBX to the outside world are converted into VoIP calls and sent over the Internet to a VoIP service provider or other VoIP peer. Calls coming from VoIP sources are converted into the appropriate legacy protocol and delivered to the PBX.