All stations common method of contacting distant monitoring and control device

摘要

PURPOSE:To ensure the second chance of reception even in the case same of the receiving stations connected to each other via a loop circuit fails to receive a selection code by transmitting a retransmission request to a transmitting station in the case no selection code is received and a command code is used for common communication among all stations. CONSTITUTION:A receiving station sends a retransmission request to a transmitting station at reception of a command code corresponding to its own station in the case a selection code is already received and the selection code is not coincident with the command code or in the case no selection code is received and the command code is used in common to all stations. The transmitting station sends successively the selection code first and then the command code when a retransmission request is received from the receiving station. Thus the second chance of reception is secured to the receiving station although it fails to receive the selection code. Then the common communication is surely ensured among all stations.