| 摘要 |
PURPOSE: A VoIP(Voice over Internet Protocol) gateway having a PSTN(Public Switched Telephone Network) transfer function is provided to offer a VoIP gateway to accept not only PSTN trunk lines but also various keyphone or PBX(Private Branch eXchange) lines. CONSTITUTION: A VoIP gateway having a PSTN transfer function is comprised of a PSTN state detection part(310), a relay(320), a PCM clock generation part(340), a SLIC(Subscriber Line Interface Circuit)/CODEC(330), an Ethernet switch(360), and a microprocessor/DSP(350). The PSTN state detection part(310) is provided to always detect a stable trunk state, regardless of line types. The relay(320) connects a generic telephone to a PSTN or the SLIC/CODEC(330). The PCM clock generation part(340) generates frame synchronization signals and PCM clocks to drive the SLIC/CODEC(330). The SLIC/CODEC(330) converts an analog voice, inputted from a generic telephone, into digital data. The Ethernet switch(360) is provided to access the Internet. The microprocessor/DSP(350), if an analog voice, inputted from a generic telephone, is converted into digital data through the SLIC/CODEC(330), executes compression/coding for the converted data and transmits the processed data to the Internet through the Ethernet switch(360).
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