| 摘要 |
PURPOSE:To prevent a system from being made large in size or complicated by using a data line and a control line of serial communication and selecting a terminal station from a central station when the mode is not in the data transmission mode so as to attain the communication of 1:n. CONSTITUTION:A central equipment 1 makes a control signal of a control line ER of a line 221 insignificant. An integration circuit 23 prevents the malfunction of a one pulse circuit 24 when noise is generated in the control line ER. Lines 221, 222 and lines 223, 224 are connected via a selector 22 and the terminal equipment 3 and the central unit 1 use a line group 200 to be in the serial communication enable state via an RS-232C interface. In sending a data from the terminal equipment 3, the RS-232C standards are applied via the lines 223 and 224. The central unit 1 and the terminal equipment 3 connected with each other are restored by making the control signal of the controlline ER insignificant again.
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