| 摘要 |
PURPOSE:To eliminate the need for the measurement of the quality of a second line or the switching of a communication line by a person by visiting a place where a modem is installed by returning the communication line from a first line to the second line after automatically confirming the recovery of the second line and the quality of the second line by the modem. CONSTITUTION:A level measuring part 15 measures the level of a specific signal from a tone transmission part 12 and transmits it to a control part 21, and the control part 21 calculates an S/N value from a measured level, and transmits the value from a command/response transmission and reception part 17. A command/response transmission and reception part 16 receiving the S/N value compares it with the S/N value set at a setting part 26, and when it exceeds a preset value, the command/response transmission and reception part 16 is connected to a private line 4 by controlling a switch 27. In such a way, when the private line is recovered and the quality of the line is kept constant, the line can be switched from a public line to the private line.
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