A dual stage plug assembly 10 which provides a first sealing stage which is cooperatively provided by the insertion members 12, 14 and a second sealing stage which is provided by selectively expandable member 24. A face member and a face support member form a duct that guides part of outside air coming in through an outside-air intake of the face member to an opening portion of the shroud panel. Based on control signals, the multiplexer circuitry can be used to select a rotation, multiplication, or barrel shifted output. A steel shank being fitted into the bore of the bolster at a bolster end of the shank, and a portion of the shank is disposed within a bore of the holder at a holder end of the shank. The two frames are joined by the pivot as well as by at least one hydraulic cylinder.