| 摘要 |
PURPOSE:To improve the efficiency of data gathering, by requesting a data gathering device for data transmission when the terminal side needs to transmit data and detecting this request to perform the polling control in the data gathering device and gathering data to the data gathering device. CONSTITUTION:When a receiving signal A from a terminal equipment has the polarity inverted, a polarity inversion detecting circuit 11 sets a polarity inversion detection signal B to ''1''. The detection signal B is inputted to a control circuit 15, and the control circuit 15 outputs a read signal R to a gate circuit 14, and the signal B from the detecting circuit 11 is read into the control circuit 15. The control circuit 15 transmits a line selecting signal C. A line selecting circuit 12 connects the transmission line to a receiving circuit 17. By the generation of the signal C, the detecting circuit 11 sets the detection signal B to ''0''. A transmission signal D is transmitted by the signal of the control circuit 15. Return data is received as a receiving signal E by the receiving circuit 17. After receiving, the line selecting circuit 12 disconnects the line by the line selecting signal C, thus terminating one polling. |
