If your Expansion Interface requires a Buffered EI cable, and your cable is either missing or malfunctioning, now you can replace it with a new one made from new components.  It even fits inside the plastic case your old Buffered EI cable came in.

For a video about the NewBUFF: https://www.youtube.com/watch?v=iexYpqT4uZM

These cables have not been available from Radio Shack since 1983.