Power transmission is the movement of energy from its place of generation to a location where it is applied to performing useful work.

Power is defined formally as units of energy per unit time.

In SI units: 1 watt = 1 joule/s = 1 newton * metre/second (1W=1J/s=1N·m/s).

Since the development of technology, transmission and storage systems have been of immense interest to technologists and technology users.

Devices for the mechanical transmission or mechanisms, constitute the basic units from which all kinds of machinery are built up. They are devices whereby certain actions can be employed when certain motions are performed. Every mechanism consist of individual elements whose movements in relation to one another are positive : i.e., the motion of one element produces an accurately determinable and definable motion of every individual point of the other elements of that mechanism. Numerous combinations and modifications are possible, but six basic types of mechanism are to be distinguished :

1. Screw mechanism : when the screw spindle is rotated, the element attached to the nut will move in the longitudinal direction of the screw. For example: vise, cross slide of a lathe, work table of a milling machine. Conversely, if the nut is rotatably mounted in the frame of the mechanism and driven, the screw spindle will move longitudinally.

2. Linkage or crank mechanism : The characteristic element is the crank, which is rotatably mounted on the frame and is usually so designed that it can be perform complete revolutions. Its motion is transmitted through the coupler or connecting rod to the lever or rocker arm, likewise rotatable mounted, but not performing complete revolutions. Alternatively, instead of being connected to a lever, the coupler may be attached to a sliding element e.g., a piston in a steam engine or internal-combustion engine.

3. Gear mechanism : This type of mechanism transmits rotary motion from one shaft to another, usually in conjunction with a change in rotational speed and torque. In a gear mechanism of the usual type the transmission is affected by the meshing of gear teeth, but in the friction-gear mechanism this positive drive is replaced by frictional contact of wheels or rollers. It is very important to conduct perodic preventive maintenance software for mechanical power transmission components, a general purpose work order software also refered as CMMS Software allows maintenance teams to control and manage assets better.

4. Pulley mechanism : Connection between the pulleys on their respective shafts is effected by flexible elements (belts, ropes, etc.)

5. Cam mechanism : A cam plate mounted on a frame is driven and thus moves a lever or slider which thus performs a desired predetermined motion depending on the shape of the cam. For example: Valve control mechanism in an internal combustion engine.

6. Ratchet mechanism : This serves to arrest a motion or to produce an intermittent rotation in the driven element. The pawl allows the ratchet wheel to rotate in one direction only, preventing rotation in the opposite direction by engaging with the specially shaped teeth on the wheel.