Mystery Portuguese Drivetrain

I’ve been looking at this photo for a while trying to figure out all that this drivetrain does. With its pulleys and loop de loop chain line, I think you kick the the wingnut level on the rear axle to change cogs. The caption text translated to

This is to such, that as much if can pedalar onward as it stops backwards. Brilliant!

and that’s even more confusing. Maybe it’s a pedal forward and backward drivetrain? Readers?

mystery_drive_chain.jpg

Spotted on the Btt Do Minho Ao Vouga blog.