Optical subscriber line terminal unit and a state transition control method

摘要

An optical subscriber line terminal unit and a state transition control method are provided which are capable of stabilizing operation. State information storing means, which is a nonvolatile memory, stores state information about the unit. Startup preparatory state shifting means causes a shift to a startup preparatory state at startup. Flag setting means sets an emergency stop state flag during the period of the startup preparatory state if it is judged based on the state information that a state before the startup is an emergency stop state. State transition control means causes a shift from the startup preparatory state to the emergency stop state if the emergency stop state flag is set, and causes a shift from the startup preparatory state to an initial state if the emergency stop state flag is not set.