<Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> A semi-automatic transmission (SAT) (also known as a clutchless manual transmission, automated manual transmission, trigger shift, flappy - paddle gear shift, or paddle - shift gearbox) is an automobile transmission that does not change gears automatically, but rather facilitates manual gear changes by dispensing with the need to press a clutch pedal at the same time as changing gears . It uses electronic sensors, pneumatics, processors and actuators to execute gear shifts on input from the driver or by a computer . This removes the need for a clutch pedal which the driver otherwise needs to depress before making a gear change, since the clutch itself is actuated by electronic equipment which can synchronise the timing and torque required to make quick, smooth gear shifts . The system was designed by automobile manufacturers to provide a better driving experience through fast overtaking maneuvers on highways . Some motorcycles also use a system with a conventional gearchange but without the need for manual clutch operation . </P> <P> In the 1930s, automakers began to market cars with some sort of device that would reduce the amount of clutching and de-clutching and shifting required in stop and go driving . Most typically, a fluid coupling or a centrifugal clutch replaced the standard manual clutch to allow for stop and go driving without using the clutch pedal every time the car was brought to a stop . More sophisticated systems allowed for shifting while driving without using the clutch, and some systems did away with the clutch pedal altogether . Semi-automatic transmissions were phased out as technology advanced and automatic controls were developed to take care of changing gear ratios . Smaller, lower powered cars used Semi-automatic transmissions with a dry clutch because the mechanical connection offered a more efficient powertrain compared to a fluid coupling . </P> <P> Another early semi-automatic transmission was the Sinclair S.S.S. (synchro - self - shifting) Powerflow gearbox. which was applied to Huwood - Hudswell diesel mines locomotives . It was also applied to some road vehicles . </P>

What is the difference between automatic and semi automatic car