A communication system is capable of two-way wireless data communications between a parent unit and a child unit. The child unit includes a power switch for turning power to the child unit on/off; a power control signal issuing unit operable to issue a power control signal for turning power to the parent unit on/off in response to turning the power switch on/off; and a data communication unit operable to perform two-way wireless data communications with the parent unit. The parent unit includes a power control signal receiving unit operable to receive the power control signal from the issuing unit of the child unit; a power control unit operable to turn power to the parent unit on/off in response to reception of the power control signal from the receiving unit; and a data communication unit operable to perform two-way wireless data communications with the child unit.