System, communications node, and switching method

A communications node comprising:

• a transmitting circuit;
• and
• a receiving circuit, wherein
• the communications node is among a plurality of communications nodes that synchronously switch between a first state and a second state,
• the communications node, when in the first state and an abnormality occurs at the communications node, transmits to a communications apparatus, a first abnormality notification signal that gives notification that the abnormality occurred, and when in the second state, the communications node transmits to the communications apparatus, a data signal that differs from the first abnormality signal,
• the communications node, during each interval of the first state:
• enters a third state during a first partial interval that is included in the interval of the first state, the communications node when in the third state, receives by the receiving circuit, a second abnormality notification signal transmitted from a second communications node among the plurality of communications nodes and transfers the second abnormality notification signal by the transmitting circuit, and
• enters a fourth state during a second partial interval that differs from the first partial interval and is included in the interval of the first state, the communications node when in the fourth state, refrains from receiving the second abnormality notification signal.

A switching method of a communications node, the method comprising:

• synchronous switching between a first state and a second state by the communications node, the communications node synchronously switching with a plurality of communications nodes;
• transmitting a first abnormality notification signal to a communications apparatus by the communications node when in the first state and an abnormality occurs at the communications node, the first abnormality notification signal giving notification that the abnormality occurred;
• transmitting a data signal to the communications apparatus by the communications node when in the second state, the data signal differing from the first abnormality notification signal;
• receiving and transferring by the communications node when in a third state, a second abnormality notification signal transmitted from a second communications node among the plurality of communications node, the communications node being in the third state during a first partial interval that is included in an interval of the first state;
• and
• refraining from receiving the second abnormality notification signal by the communications node when in a fourth state, the communications node being in the fourth state during a second partial interval that differs from the first partial interval and is included in the interval of the first state.