Matthew,
"Porta Catena" (i.e. Chain Carrier) is what the seller means. It's hard to desctibe how the setup works, so here's a photo that a list member pointed out earlier in the year:
http://media.photobucket.com/
The metal piece mounted between the small freewheel sprocket and the dropout is the "Porta Catena". The idea is to shift the chain onto this piece before removing the rear wheel. That requires the shifter to handle an extra position, albeit one that you don't want to use inadvertently. Hence the extra little lever attached to the main rear shift lever. That is, it's the lock-out which prevents the rider from shifting onto the Porta Catena during normal riding.
I hope this made sense...
Fred Rednor - Arlington, Virginia (USA)
> From: devotion finesse <devotion_finesse@hotmail.com>
\r?\n> Subject: [CR]Can somebody please explain this Campy oddity?
\r?\n> To: "CR discussion list" <classicrendezvous@bikelist.org>
\r?\n> Date: Tuesday, August 5, 2008, 9:38 PM
\r?\n> A "Porta Cantina" downtube shifter?
\r?\n> I have never heard of or seen such a shift lever:
\r?\n>
\r?\n> http://ebay.com/
\r?\n> itemZ220264053177QQihZ012QQcategoryZ36140QQssPageNameZWDVWQQrdZ1QQcmdZViewI
\r?\n> tem
\r?\n>
\r?\n> Can someone please explain their function to this
\r?\n> "newbie"?
\r?\n>
\r?\n> Thanks, Gang!
\r?\n>
\r?\n> Matthew Bowne
\r?\n> Brooklyn, New York 11222