A transmission device comprising: a first control unit that outputs transmission data including an identification signal, the identification signal being unique to the transmission device; a signal transmission unit that receives the transmission data and converts the transmission data to a first frequency signal and a second frequency signal having a frequency different from a frequency of the first frequency signal, characterized in that the transmission device further comprises: a receiver that receives a third frequency signal generated based on the transmission data and having a frequency different from the frequency of the first frequency signal and the frequency of the second frequency signal, converts the third frequency signal to a reply receipt signal, and outputs the reply receipt signal to the first control unit, wherein in a case where the reply receipt signal is not detected in a first time after output of the transmission data to the signal transmission unit, the first control unit outputs the transmission data again to the signal transmission unit as first retransmission data after a lapse of a first standby time since the first time has elapsed, and wherein in a case where the reply receipt signal is not detected in a second time after output of the first retransmission data to the signal transmission unit, the first control unit outputs the transmission data again to the signal transmission unit as second retransmission data after a lapse of a second standby time since the second time has elapsed, wherein the first control unit sets the first standby time and the second standby time based on the identification signal in such a manner that the first standby time and the second standby time differ from each other. a first control unit that outputs transmission data including an identification signal, the identification signal being unique to the transmission device; a signal transmission unit that receives the transmission data and converts the transmission data to a first frequency signal and a second frequency signal having a frequency different from a frequency of the first frequency signal, characterized in that the transmission device further comprises: a receiver that receives a third frequency signal generated based on the transmission data and having a frequency different from the frequency of the first frequency signal and the frequency of the second frequency signal, converts the third frequency signal to a reply receipt signal, and outputs the reply receipt signal to the first control unit, wherein in a case where the reply receipt signal is not detected in a first time after output of the transmission data to the signal transmission unit, the first control unit outputs the transmission data again to the signal transmission unit as first retransmission data after a lapse of a first standby time since the first time has elapsed, and wherein in a case where the reply receipt signal is not detected in a second time after output of the first retransmission data to the signal transmission unit, the first control unit outputs the transmission data again to the signal transmission unit as second retransmission data after a lapse of a second standby time since the second time has elapsed, wherein the first control unit sets the first standby time and the second standby time based on the identification signal in such a manner that the first standby time and the second standby time differ from each other. a receiver that receives a third frequency signal generated based on the transmission data and having a frequency different from the frequency of the first frequency signal and the frequency of the second frequency signal, converts the third frequency signal to a reply receipt signal, and outputs the reply receipt signal to the first control unit, wherein in a case where the reply receipt signal is not detected in a first time after output of the transmission data to the signal transmission unit, the first control unit outputs the transmission data again to the signal transmission unit as first retransmission data after a lapse of a first standby time since the first time has elapsed, and wherein in a case where the reply receipt signal is not detected in a second time after output of the first retransmission data to the signal transmission unit, the first control unit outputs the transmission data again to the signal transmission unit as second retransmission data after a lapse of a second standby time since the second time has elapsed, wherein the first control unit sets the first standby time and the second standby time based on the identification signal in such a manner that the first standby time and the second standby time differ from each other.