Abstract: An indoor unit included in an air conditioner that includes an outdoor unit includes a power receiving circuit (PR2), a low-frequency transmission and reception circuit as a first reception circuit, a high-frequency transmission and reception circuit as a transmission and reception circuit, and an inner-controller. The low-frequency transmission and reception circuit receives a current signal transmitted from an outdoor unit by using a current loop formed by a power line included in power supply wiring. For a first communication state in which physical connection between with the outdoor unit is recognized and a second communication state in which communication for operation of the air conditioner is performed between with the outdoor unit, the inner-controller selects use of the low-frequency transmission and reception circuit and the high-frequency transmission and reception circuit in the first communication state and the second communication state.

Abstract: A device management system is equipped with a storage section, a detecting component, and a calculating component and manages an installation device. The storage section stores operating rules of the installation device. The detecting component detects a violating action of the installation device running counter to the operating rules. The calculating component calculates a violating quantity that quantitatively expresses the violating action.

Abstract: A device management system is equipped with a storage section, a detecting component, and a calculating component and manages an installation device. The storage section stores operating rules of the installation device. The detecting component detects a violating action of the installation device running counter to the operating rules. The calculating component calculates a violating quantity that quantitatively expresses the violating action.