In CNX80 User Newsletter number 1 at

http://www.garmin.com/manuals/GNS480...st_Edition.pdf

on page 5, the author refers to "... a 'happy-box' that accepts the roll
steering output commands from the CNX80 and turns them into voltage outputs that
mimic the inputs from the HSI/DG heading bug."

I haven't found any other information about such a device. Anyone?

Thanks.

Dave