Abstract: A common package serves as, for example, a common network interface package for a switching system. Since the common package is usable for various purposes, its cost is reduced and the cost of maintenance and management of the switching system is reduced. The common package is a printed board package (35) installed in an apparatus and used for a variety of purposes. The common package includes a programmable device (36), memories (45 to 48) for storing programs to configure the programmable device, a selector (41) for selecting one of the programs from the memory so that the selected program may so configure the programmable device as to make the common package serve as a specific circuit, and an instruction unit (51) for issuing an instruction to specify the program to be selected by the selector.