Abstract: An interface device having a printed circuit board connected to a processor unit and an electronic base with grooves to receive the board with active or passive interface devices connected by terminal blocks. The interface devices are housed in separate modules having lengths which are equal to or integer multiples of a modulus wherein each module includes a strip of indicator openings or terminal operating openings disposed lengthwise at a particular pitch. The modules have complementary grooves and tongues on their side faces in order to permit assembly perpendicular to the plane of the board thereby forming a rigid assembly.