| 摘要 |
PURPOSE:To select a transmission line in accordance with a condition by changing over a digital transmission network to an analog transmission network based upon the trouble reason responded from a digital transmission network at the time of calling an address with use of the digital transmission network and a call loss occurs. CONSTITUTION:When an address is designated from an operating displaying part 9 by an operator, a system control part 7 reads the address information from an address information memory part 8, communicates it to a network control device 4, calls the address by a digital line network DX and starts the data transmitting procedure to a communicating control part 2. To such a state from a digital line network DX, the connecting completing information or the cutting instructing information including the reason why the call cannot be connected are responded. When the system control part 7 investigates the contents of the responding information, a line changing-over flag is on and the usable data of an analog line network AX are stored into the address information, communication is executed to a network control device 6, the address is called by an analog line network AX and the data transmission procedure is started by a communicating control part 3.
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