PURPOSE: To make an exchange frame small by plugging in private lines, trunk lines or exclusive lines directly to a multi-jack connector of a printed circuit board provided with an interface circuit so as to connect the wires to an internal wiring of the exchange.

CONSTITUTION: An interface circuit between an external line and an exchange internal wiring is provided to a printed circuit board 3 and a multi-jack connector 20 with lots of housing cells 23 arranged therein is mounted to a front side of the printed circuit board 3. Then a plug connector 30 is mounted respectively to terminals of interconnection wiring 8 and of trunk lines 9 and each connector 30 is plugged into a selected cell 23 of the connector 20 to connect the external line to the printed circuit board 3 directly. Thus, the change of the accommodation of the external line is executed by selecting a cell 23. Moreover, the external line and the interface circuit are disconnected by taking out the connector 30. That is, the function of the main wiring board of the exchange is entirely provided.