| 摘要 |
PURPOSE:To improve the line efficiency, by detecting a failure of a slave station through timeout to polling and performing status polling shorter in timeout at the failure, in transmitting signals through alternate monitor between a master station and slave stations. CONSTITUTION:When no answer A is returned in a timeout T to a polling P to the slave section 2, it is discriminated that the slave station 2 is failed and the mode is switched to the emergent mode as (B). If no response R is returned within a timeout T2 (<T1) to the status polling SP, it is discriminated that a failure continues, the emergent mode is kept, and when the response R is returned within the timeout T2, it is discriminated that the failure is recovered and the mode is switched to the normal mode (A). |
