Abstract: A private branch exchange includes a common control module and a plurality of line/trunk modules. A plurality of line/trunk cards are contained in a respective line/trunk module and terminals of the same type, such as digital telephones or standard telephones, are connected to the respective cards. For control data transmission, the line/trunk cards of each of the line/trunk modules are coupled to the common control module via a common control data highway. Each line/trunk card includes, for terminal control, a central processor unit (CPU) and random access memory (RAM) for storing a control program in accordance with the type of terminals. To the line/trunk card is allocated an individual address and group address representing a group of line/trunk cards to which are connected terminals of the same type.