SAFETY NETWORK SYSTEM AND SAFETY SLAVES AND SAFETY CONTROLLER AND COMMUNICATION METHOD AND INFORMATION GATHERING METHOD AND MONITORING METHOD IN SAFETY NETWORK SYSTEM

摘要

A safety PLC 1 and at least a safety slave unit 2 are connected through a safety network 3. The safety slave unit has the safety information transmission function for transmitting the safety information for determining whether a safe state prevails or not and the unsafety information transmission function for transmitting the unsafety information containing no safety information. The unsafety information transmission function transmits the unsafety information on condition that the safety slave unit is in a safe state. Specifically, in the case where it is determined that no safe state prevails at the timing of transmitting the unsafety information, the unsafety information is not sent but the safety is transmitted. A safety controller, upon receipt of the unsafety information, estimates that the safety slave unit at the transmitting end of the particular unsafety information is in a safe state. <IMAGE>