| 摘要 |
PURPOSE:To enable to reduce the amount of signal transfer, by the transmission of selected sequence only from a single slave station located nearest the control station side to establish the data link, in a multidrop data communication system of contention system. CONSTITUTION:When data transfer request is produced at slave stations 112, 113... 11n, the terminal (c) of respective selector switches 152, 153...15n is switched from the terminal (b) to the terminal (a). Further, when no character sequence is transferred to transmission line 12 and reception line 13, a control station 14 outputs the control signal of ''L'' to a control 17. Further, the terminal (c) of the switch 15 is connected to the terminal (a) to hold ''H'', then the slave stations 113...11n transmit no selected sequence. Moreover, although the terminal (b) of the switch 151 is at ''L'', an AND circuit (not shown) has no AND condition, and the slave station 111 does not transmit the selected sequence. Accordingly, the reduction in the amount of signal transfer can be made by establishing the data link through the transmission of selected sequence by the slave station 112. |
