The invention provides a communication apparatus used inside a house, a communication system connected thereto, a communication process, and computer program used therefore. The communication apparatus of the present invention connected via a network to one or more terminal appliances in the house, communicates with the outside via two or more different communication configurations including a first communication configuration with a high speed digital transmission technique and a second communication configuration providing service for telephone subscribers. The communication apparatus is characterized in recognizing a situation thereby to disconnect the first communication configuration and to use only the second communication configuration for communication with the outside.