cone pulley

Some motors have electronic rheostat-type speed controls, which obviates cone pulleys or gears.

Different spindle speeds could be obtained by moving the flat belt to different steps on the cone pulley.

Therefore early engine lathes were generally 'cone heads', in that the spindle usually had attached to it a multi-step pulley called a cone pulley designed to accept a flat belt.

Various types of speed-changing mechanism achieve this, from a cone pulley or step pulley, to a cone pulley with back gear (which is essentially a low range, similar in net effect to the two-speed rear of a truck), to an entire gear train similar to that of a manual-shift auto transmission.