| 摘要 |
PURPOSE:To relieve the load of a master station by allowing a slave station not receiving a signal from a host station until an estimated time to send an inquiry signal in the slave station of a system where the inquiring signal is transferred sequentially from a master station to plural salve stations. CONSTITUTION:The master station sends an inquiry signal to a slave station 1 only via a branch device 13 and a route 2 from a route 1. The slave station 1 returns the signal to the master station when a reply signal exists, but transfers the inquiry signal to a slave station when no reply signal exists, and a slave station 4 sends a signal finally to the master station. The slave stations 2-4 monitor the inquiry signal to the slave station 1 and sets a required time of a signal transferred to the own station from the point of time to a timer. When a timer is over until the signal is transferred from a high-order station, it is regarded that the inquiry signal comes from the high-order station and the inquiry signal is sent to a low-order station. Thus, the load of the master station is relieved and the inquiry signal is prevented from being vanished even if a fault takes place in a slave station.
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