In the world of mechanical power transmission, gear drives employ a special and prominent place. This is the the majority of preferred technology 
when you need to transmit considerable power over a brief distance with a continuous velocity ratio. The mechanism of gear drives is fairly simple - the teeth, which are cut on the blanks of the apparatus wheel, mesh with each other to transmit power. In order to avoid gear chain china slipping, the projections on one disc mesh with the recesses on other disc in gear drives.
This technology uses different types of gears for power transmission. Actually, it can transmit power not only between parallel shafts, but also between nonparallel, co-planar, and intersecting etc. shafts.