An AEC signal is transmitted and received always in a wireless manner between a wireless communicator of an electronic cassette and a wireless communicator of a control device, regardless of the presence or absence of wired communication. If communication failure occurs in the wired communication and X-ray image data cannot be transmitted in a wired manner, a memory of the electronic cassette temporarily stores the X-ray image data. Since the AEC signal is wirelessly transmitted, X-ray imaging is continued even if the wired communication is unusable. A cause of the communication failure is more easily identified in wireless communication than in the wired communication. Thus, even if the communication failure occurs in the wireless communication, the wireless communication quickly recovers from the failure and downtime of an X-ray imaging system does not become too long.
