| 摘要 |
PURPOSE:To reduce the detection time and to increase the reliability, by rejecting the common circuit section such as scanner of the vacant line detection circuit detecting the vacant time of communication path unit and using the logic elements such as simple AND gates in combination. CONSTITUTION:The logic gate circuits 7-9 detecting the vacant logic level 0 of a plurality of information signal input terminals X1-X3 is connected between the priority designation circuit 10 and the vacant information reception number generating circuit 11 to constitute the vacant signal line detection circuit. To each of the circuits 7-9, the NAND gates 72, 73, 75, 82, 83, 85 and 92, 93, 95 outputting the vacant information and designation signal with the vacant signal at the input terminals X1-X3 and the control signal from the circuit 10 are provided, and they are in cascade connection cyclicly so that the designation signal outputted from the gates 73, 83 and 93 which are one of the output side can be the control signal to the next stage. The gates 75, 85, 95 take the logic between the priority signal and designation signal from the line 10, and only one vacant information in a plurality of vacant information sets is outputted to the generation circuit 11 via the gates 72, 82 and 92. |
