Richard, Sasha and All Youse Anklers,
The idea was to have a 'idle' gear for quick wheel changes - in theory.
Porta Catena requires five speeds with the sixth being the 'idle' position. The PC shifter is a regular Super/Nuovo but with a release switch to drop the derailleur the required amount under the trough.
I have a NOS set up I keep meaning to install, but haven't - but apparently it doesn't work so great and seems to me to be a solution searching for a problem - which probably explains it's short stay in the Campy line-up. Anyway, I will return to daily contemplating whether or not to open my set-up which includes a shift lever and the trough to bolt on at the drop outs.
Here's a picture: http://www.flickr.com/
As for storage here's what works for me:
http://www.flickr.com/
-Harry Schwartzman
Brooklyn, NY