Redundancy device, redundancy system, and redundancy method

A redundancy system comprising:

• a first device;
• and
• a second device which is configured to communicate with the first device and perform a redundancy execution,
• wherein the second device comprising:
• receivers configured to receive individually HB signals transmitted from the first device;
• a calculator configured to calculate a number of normal communication paths among communication paths of the HB signals based on a reception result of the receivers;
• a comparator configured to compare a calculation result of the calculator with a predetermined threshold value;
• and
• a changer configured to change the second device from a standby state to an operating state, or change the second from the standby state to a not-standby state in which the redundancy execution is released, based on the calculation result of the calculator and a comparison result of the comparator.

A redundancy method for a redundancy system which comprises a first device and a second device which is configured to communicate with the first device and perform a redundancy execution, the redundancy method comprising:

• receiving, by the second device, individually HB signals transmitted from the first device;
• calculating a number of normal communication paths among communication paths of the HB signals based on a reception result of the HB signals;
• comparing a calculation result of the number of normal communication paths with a predetermined threshold value;
• and
• changing the second device from a standby state to an operating state, or changing the second device from the standby state to a not-standby state in which the redundancy execution is released, based on the calculation result and a comparison result.