Abstract: An air conditioning control system includes a plurality of remote control terminals and a server. The plurality of remote control terminals each calculates a time required for a user of the remote control terminal to return to a building from outside the building, and transmits information indicating the time required to the server. The server calculates an estimated time when a user who returns to the building first among the plurality of users returns to the building on the basis of the time required, and transmits a command for changing air conditioning setting to an air conditioner in stages from a time when the estimated time is calculated to the estimated time calculated.

Abstract: An air conditioning control system includes a plurality of remote control terminals and a server. The plurality of remote control terminals each calculates a time required for a user of the remote control terminal to return to a building from outside the building, and transmits information indicating the time required to the server. The server calculates an estimated time when a user who returns to the building first among the plurality of users returns to the building on the basis of the time required, and transmits a command for changing air conditioning setting to an air conditioner in stages from a time when the estimated time is calculated to the estimated time calculated.

Abstract: In a communication device, a communicator communicates with a communication counterpart using a first communication mode or a second communication mode. When a communication by the communicator with the communication counterpart using the second communication mode is reset due to a first cause, if the communication with the communication counterpart using the second communication mode is acceptable, a communication controller causes the communicator to resume communication with the communication counterpart using the second communication mode, and if the communication with the communication counterpart using the second communication mode is unacceptable, the communication controller causes the communicator to start a communication with the communication counterpart using the first communication mode.

Abstract: An air conditioner connection system includes an air conditioner having a first device connected via a power line in a communication-capable manner, and a second device capable of performing radio communication with the air conditioner. The air conditioner includes an authentication process control unit that controls the first device to perform an authentication process when a starting request of the authentication process for performing power carrier communication is received from the second device, the first device includes an authentication process unit that performs the authentication process under the control of the air conditioner, and the second device includes an authentication start process unit that transmits the starting request of the authentication process to the air conditioner.

Abstract: In a communication device, a communicator communicates with a communication counterpart using a first communication mode or a second communication mode. When a communication by the communicator with the communication counterpart using the second communication mode is reset due to a first cause, if the communication with the communication counterpart using the second communication mode is acceptable, a communication controller causes the communicator to resume communication with the communication counterpart using the second communication mode, and if the communication with the communication counterpart using the second communication mode is unacceptable, the communication controller causes the communicator to start a communication with the communication counterpart using the first communication mode.

Abstract: An air conditioner connection system includes an air conditioner having a first device connected via a power line in a communication-capable manner, and a second device capable of performing radio communication with the air conditioner. The air conditioner includes an authentication process control unit that controls the first device to perform an authentication process when a starting request of the authentication process for performing power carrier communication is received from the second device, the first device includes an authentication process unit that performs the authentication process under the control of the air conditioner, and the second device includes an authentication start process unit that transmits the starting request of the authentication process to the air conditioner.