A Swiss automatic watch is wound through the natural motion of the wearer's arm. Automatic watches are distinguished from manual watches and electric watches, both of which work differently.
All mechanical watches are powered by an internal device called a mainspring. Throughout the day, the mainspring slowly unwinds, turning the gears that power the watch. In a manual watch, the mainspring must be periodically recharged by turning a small knob on the outside of the case of the watch. A self-winding, or automatic, watch contains a small, unbalanced weight called the rotor. The natural action of the wearer's wrist causes the mainspring to continually rewind, recharging the watch without further action. The watch also contains a device to prevent over-winding of the mainspring so that it is not damaged.
The first self-winding wristwatch was invented in 1923 by an English watch repairer named John Harwood. The design was later improved upon by the famed English-Swiss Rolex Watch Company. Since the 1960s, the self-winding watch has been the standard for fine watch making in Switzerland and elsewhere, though certain companies still use manual designs because they are thinner. Since the 1960s, electric quartz watches have also become popular due to their relatively simpler design and greater accuracy.