A gear rate reducer is a representative example of acceleration changers, and presently used systems could be categorized by the kind of gears, shaft positions and arrangement of gears into (1) gear reducer with parallel axes, (2) equipment reducer with orthogonal axes, (3) equipment reducer with perpendicular non-intersecting axes, and (4) gear reducer with coaxial axes.

Types and mechanisms of gear reducers with parallel axes
The apparatus reducers with parallel axes use spur gears, helical gears, or herringbone gears. Their input and output shafts are parallel. As for reduction ratios, 1/1 – 1/7 for one-stage shafts, 1/10 – 1/30 for two-stage shafts, and 1/5 – 1/200 for a lot 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 tranny efficiency is very high. (98 to 95% for one-stage equipment reducer)
When properly lubricated, it can be utilized for a long period.
Could be produced relatively cheaply because standardized gears are used.
Gear reducers with spur gears are used for increasing swiftness.
The sizes of gear reducers with spur gears are is generally large. Compared to worm equipment reducers with the same quickness ratio, their outer styles are huge, and the number of parts increases leading to constructional disadvantages. As a result, it can be used for planetary gearbox machines with high rotation on the load side, or which need higher output rotation than the prime movers (for increasing velocity). The apparatus types are demonstrated in Table 2.1.

The apparatus reducers with parallel axes usually use helical gears. They are used in steel services, ships, cranes, elevators, and conveyors. For automation machines, these gear reducers are also known for geared motors which are equipment reducers with directly connected motors.