Copyright jalopnik
An automated manual transmission (AMT) is the simplest of all semi-automatic gearboxes. It is a basic manual gearbox where actuators control the clutch and gearshifts. Some examples are the AMT gearbox in the India-spec Maruti Suzuki Alto or the intelligent manual transmission (iMT) in the India-spec Hyundai i20. While AMTs can act as fully automatic transmissions, iMTs require driver intervention to change gears. These gearboxes are used mainly in low-priced cars for their simplistic build and low-cost nature. These gearboxes are easy to make, cheap to run and maintain, and fuel efficient, though some dislike them for their slow and abrupt shifts. Then you have the sequential semi-automatic gearboxes, which can be seen in some high-performance sports cars. Like motorcycles, these gearboxes shift in sequence and you can't skip gears. Some common examples are BMW's Sequential Manual Gearbox (SMG) and Ferrari's 355 F1 semi-automatic transmission. These gearboxes have powerful hydraulic actuators and precise electronics for lightning-fast shifts. They're great for the racetrack but can feel tedious in stop-and-go traffic, due to their harsh shifts. The dual-clutch transmission (DCT) is the next step in the evolution of the semi-automatic gearbox. It follows the same philosophy in that it allows you to shift gears manually without the need for clutch inputs. The primary difference is the DCT's use of two clutches instead of one. The DCT uses one clutch for even gears and one for odd gears. So, when you are in second gear, the gearbox has already pre-selected third gear with the clutch disengaged. Then, when you shift to third, the gearbox simply disengages the second gear's clutch and engages the third gear's clutch, effectively and rapidly shifting you into third gear.
