| 摘要 |
PURPOSE: A data communication network system using part of a PSTN and a signal processing apparatus used therein are provided to construct a data communication network using a special key network and a PSTN(Public Switched Telephone Network) incoming line. CONSTITUTION: A data communication network system comprises a central unit(31) connected to an Internet communication service provider's hub(332) and a subscriber unit(32) connected to a subscriber's PC(342). The central unit(31) and the subscriber unit(32), connected each other through a PSTN incoming line(35), have a symmetrical configuration. Each comprises transmitters(311,321) transmitting signals through the PSTN incoming line(35) and receivers(312,322) receiving signals through the PSTN incoming line(35). Also the units(31,32) respectively comprise switch controllers(317,327) that alternately open and/or close the switches(315,316) of the transmitters(311,321) and the switches(325,326) of the receivers(312,322) in order to prevent a transmit signal and a receive signal from colliding each other. Also each unit comprises a mixer(318,328) and a divider(319,329). The mixer(318,328) mixes a voice signal with a data signal and transmits the mixed signal through the incoming line(35). The dividers(319,329) divide a voice and data signal received through the PSTN incoming line(35).
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