| 摘要 |
PURPOSE:To constitute a delivery circuit of only one asynchronous system transmission circuit, by switching and transmitting a signal transmitted from a signal transmission circuit of asynchronous system to a network control unit(NCU) and a modem device by a switching circuit. CONSTITUTION:The NCU30 sends a dial signal to a telephone line according to a dial number sent from a transmission part 10, and when the line is connected to an information center, a video tex switching instruction signal is sent from the information center. When an information processing part 1'' recognizes the video tex switching instruction signal, the output signal of a switching signal generating part 34 is set at an (L) level. An OR circuit 37 opens a gate, and the output signal of the transmission part 10 is transmitted to a modem, and it is modulated by the modem, and is set as the up signal of a video tex. Thus, by providing the switching circuit 38 which switches the signal of asynchronous system outputted from the transmission part 10, it is possible to permit to prepare only one delivery circuit for an asynchronous signal.
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