Control apparatus and control method for managing communications between multiple electrical appliances through a household power line network

The present invention relates to a control apparatus for managing communications between a plurality of electric appliances connected to a household power line network. The apparatus transmits a plurality of types of modulation method control signals to each of the plurality of electric appliances, each type of control signal utilizing a different modulation method. When receiving a response from each electric appliance, the apparatus detects to which type of modulation method control signal the response was made and judges the type of the modulation method that is utilized in each electric appliance based on the detection.