| 摘要 |
PURPOSE: A method for establishing a communication link between different networks is provided to reduce dependency on the communication agreement of an external PSTN network not to changer the agreement of inner network even if the communication agreement of PSTN network is changed. CONSTITUTION: A message demanding connection is transferred to a gateway through a signal channel in an inner network. Then, the gateway receiving the message demanding connection establishes a link between an outer and an inner network for opening a voice channel, and signal inputted through the voice channel of the outer network is packetted in the gateway for being inputted to the inner network. A target address outputted from the inner network through a signal channel is converted into a certain signal in the gateway for outputting to the outer network. And, a ring back tone or a busy tone of the outer network is packetted to be transferred to the voice channel in the inner network. When a voice is inputted, the voice is packetted for being transferred to the voice channel of the inner network. When the inner network receives connection refusal signal, a connection releasing message is transferred to the gateway for closing the voice channel and for releasing the link to the outer network.
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