| 摘要 |
PURPOSE:To attain efficient maintenance of an exchange by connecting a 2-way link of a digital line to be monitored to an acoustic monitor via an adder circuit. CONSTITUTION:When a maintenance personal of the exchange monitors a talking line, a signal from an output channel of a digital subscriber circuit 5 and from an output channel of a digital interface trunk 11 is connected to a digital 3-party conference trunk 7 operated as an adder circuit. A monitor subscriber circuit 9 converts a digital signal into an analog signal by a digital-analog conversion circuit 8 and sends the signal to a maintenance subscriber line. The maintenance personnel monitors the 2-way talking state of a designated digital line by using a receiver 3 connected to the maintenance subscriber line to monitor it.
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