| 摘要 |
PURPOSE: An automatic switching system of a PSTN(Public Switched Telephone Network) and a leased line network is provided to perform automatically a switching operation of a leased line to the PSTN or the PSTN to the leased line. CONSTITUTION: The first line switching portion(104) switches a transmission path of digital data transmitted from the first terminal interface portion(90) to a PSTN when an error is generated from a digital data service network(110). The first line switching portion(104) switches the transmission path to the first terminal interface portion(90) when the digital data service network(110) is in a normal state. The first modem portion(105) modulates the data transmitted from the first terminal interface portion(90) through the first line switching portion(104) or demodulates the data transmitted from the second data terminal(150) through the PSTN. The first control portion(102) controls automatic switching operations and a modulating operation and a demodulating operation of the first modem portion(105).
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