| 摘要 |
PURPOSE:To reduce the scale of hardware without requiring a high-precision filter for a receiving circuit, by sending a priority request and information on a power failure by a common informaton signal and by recognizing that a subordinate station has a power failure when no data is sent withing a constant time. CONSTITUTION:A priority request signal c1 and a power-failure information signal d1 are ORed by an OR circuit 28 to be inputted as a common information signal to an information signal transmitter 29, thereby transmitting it to a master station 1 as a signal of an information signal transmission band. This information signal e1 is received by an information signal receiver 17 of the master station 1 and then fetched in a master-station logical circuit 11. Then, the circuit 11 judged the signal e1 as a priority request signal ci and sends a call signal a subordinate station (i). When the information signal is judged to be the priority request signal, data is sent from the subordinate station (i) and priority data fetching operation is carried out. When the information signal is judged to be the power-failure information signal, it is impossible to send the data in response to the call because the subordinate station (i) has the power failure, and then the master station monitors the data response time of the subordinate station to recognize the occurrence of the power failure to display that. |
