Communication system and data communication method

摘要

A communication system of this invention is constituted by a controller which accommodates a plurality of extensions connected to an office line and telephones, and includes a facsimile unit for performing facsimile communication with another communication apparatus through the office line, and a plurality of telephones connected to the extensions. The controller can inform an operation state during facsimile communication to the connecting telephone. The operation state of the facsimile unit can be recognized at the telephone. Information received by the facsimile unit can be confirmed at the telephone, and some data received by the facsimile unit can be controlled by the telephone. A registration result of an index number can be commonly used by the telephone and the facsimile unit.