A gear swiftness reducer is a representative exemplory case of quickness changers, and presently used systems can be categorized by the kind of gears, shaft positions and set up of gears into (1) equipment reducer with 
parallel axes, (2) gear reducer with orthogonal axes, (3) equipment reducer with perpendicular nonintersecting axes, and (4) equipment reducer with coaxial axes.
Types and mechanisms of gear planetary gearbox reducers with parallel axes
The apparatus reducers with parallel axes use spur gears, helical gears, or herringbone gears. Their input and result shafts are parallel. For decrease ratios, 1/1 - 1/7 for one-stage shafts, 1/10 - 1/30 for two-stage shafts, and 1/5 - 1/200 for more than three-stage shafts are commercially obtainable. The general characteristics of gear reducers with parallel axes are as follows :
For high precision gears, the transmission efficiency is very high. (98 to 95% for one-stage gear reducer)
When correctly lubricated, it can be used for a long time.
Can be produced relatively cheaply because standardized gears are used.
Gear reducers with spur gears are used for increasing rate.
The sizes of gear reducers with spur gears are is usually large. In comparison to worm gear reducers with the same quickness ratio, their outer styles are large, and the number of parts increases resulting in constructional disadvantages. Therefore, it is utilized for devices with high rotation on the strain side, or which need higher output rotation than the prime movers (for increasing quickness). The gear types are proven in Table 2.1.
The apparatus reducers with parallel axes usually use helical gears. They are used in steel facilities, ships, cranes, elevators, and conveyors. As for automation machines, these gear reducers are also known for geared motors which are gear reducers with directly linked motors.