In a system and method of communication between circuit mode units interconnected by point-to-point circuits in a subnetwork at the core of a communication installation the point-to-point circuits between units are structured and managed identically. A communication circuit is incorporated in each unit of the subnetwork, irrespective of the control unit, auxiliary unit or telephone and/or communication terminal interface controller type. This communication circuit handles the broadcasting over the point-to-point circuits to the other units of data from time-division multiplex circuits connected to it and switching of bytes addressed to it over the circuits.