Communication device and plug-in unit therefor

A communication device includes a sub-rack unit and a plurality of plug-in units. The sub-rack unit includes a back wiring board having first connectors arranged in lines thereon, and a frame plate including vertical ribs and placed on said back wiring board so that the vertical ribs separate the lines of the first connectors. Each of the plug-in units includes: a printed board including top and bottom sides and parallel first and second sides, the printed board having second connectors provided on the first side thereof; a metal case including top and bottom faces, and parallel first and second side faces so as to cover the printed board; and first and second spring members. Each of said plug-in units is mounted in the sub-rack unit with the first and second connectors being connected so that the first and second side faces of the metal case are pressed outward against the vertical ribs of the frame plate by resilient forces of the first and second spring members, respectively.