Just received my K-27 a few days ago. The Dummy Plug has J1-5 for Chuff input. However ,the sound system that I normally use is Sierra Sound which expects two chuff wires to be closed to complete a loop. What is the contact for the second chuff sound wire?. Actually I tried all of them, but none worked. This may be related: My K-27 came with two shinny black disks in a small plastic bag. No mention of these disks appear in any of the written material or diagrams. What are their purpose?