In the world of mechanical power transmission, gear drives employ a special and prominent place. This is the the majority of preferred technology if you want to transmit substantial power over a brief distance with a constant velocity ratio. The system of gear drives is very simple – the teeth, which are cut on the blanks of the gear wheel, mesh with one another to transmit power. To avoid slipping, the projections on one disc mesh with the recesses on various other disc in gear drives.
This technology uses various kinds of gears for power transmission. Actually, 
it could transmit power not merely gear chain china between parallel shafts, but also between non-parallel, co-planar, and intersecting etc. shafts.