A gateway sits between a telephone system, such as a PBX or a central office switch, and a data network, such as the Internet, and translates calls from one format to another.

• 网关置于电话系统（如专用小交换机或者电话局内的交换机）和数据网络（如因特网）之间，把电话呼叫从一种格式变成另一种格式。