The Talgo Pendular (Talgo IV and Talgo V, also VI & Talgo 200 or 6th generation), introduced in 1980, created the "natural tilting" train, using a passive system that tilts the carriages with no need for electronic sensors or hydraulic equipment. The wheels are mounted on monoaxles between the carriages, and sitting on top of the monoaxles are suspension columns. The carriages are attached to the top of the suspension columns and swing outwards as the train goes through a curve.