| 摘要 |
PURPOSE:To eliminate the error of reception data recognition by sending a reset signal having a polarity initializing the switching state of a reference voltage while being superimposed on the reset signal on a signal line before a reception data is extracted by a comparator. CONSTITUTION:When a selector 11 selects a slave set 2 by the control of a CPU, the operations such as transmission of a control data from a data transmission/reception section SR 12, the reception of the data by the SR 21, the transmission of an operation data from the SR 21 by the control of a CPU 24 at the slave set 2 and the reception by the SR 12 is performed through a signal line 3 via transformers T1, T3, and a CPU 15 controls a channel switch 13 according to the content. Thus, a talking circuit 22 is subjected to exchange connection via transformers T2, T4 and a talking line 4, the talking by the circuit 22 is performed and the slave set 2 is displayed in response to the reception of the control data by the CPU 24 via a data transmission/reception section 21. Before a data is extracted from the comparator of the transmission/reception section 21, a reset signal is sent to initialize the comparator thereby avoiding the mis-recognition of the reception data.
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