| 摘要 |
PURPOSE:To surely and easily perform call operation by a terminal by providing a means for supervising the loop closing of an external terminal equipment, a means for converting the information of the closing state into line access data and a means for connecting a main channel and the terminal equipment to a key telephone set and further providing a control means to a master equipment. CONSTITUTION:In using a DTE as an external terminal equipment, an MDM added with a function of an NCU (line network control unit) is interposed, and a modulator- demodulator MDM applies the closing of a DC loop by connecting the data terminal equipment DTE to a key telephone set 3 in response to the control of the DTE. It is detected by a loop monitor circuit 20 and the information is converted into line access data by the control section 21 and sent to the master equipment. The control means of the master equipment acquires an idle line based on the said data and sends the control data to the key telephone set to close the circuit between the channel and the MDM, and the MDM and the line stared in the master set are connected directly and various procedures till the dialing and the start of communication with an opposite party in response to the MDM based on the control of the DTE are applied smoothly and automatically.
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