Abstract: A communication control system comprises a communication control unit and a line control unit coupled to it. The former communicates with a data processor and the latter communicates with a plurality of modems. A first address signal generator in the communication control unit sends an address signal to a first decoder in the line control unit, allowing it to select one of the line adapters in the line control unit and, therefore, one of the modems coupled to the line adapter. The selected line adapter sends a signal and data if any to the communication control unit, which send a signal and data, if any, to the line control unit in response to a signal or data sent from the line control unit. A second address signal generator in the communication control unit begins to send a little later the second address signal which is the same as the first address signal to a second decoder in the line control unit, allowing it to select the same one of the line adapters as one previously selected by the first decoder.