Hydraulic and pneumatic devices are types of power transmission systems used in a variety of applications, including construction equipment, industrial machines, and transportation vehicles.

Hydraulic devices use a fluid, typically oil, to transmit and control power. The fluid is pressurized by a pump and then directed through a system of valves and actuators to perform work, such as lifting a load or controlling the movement of a machine. Hydraulic systems are commonly used in construction equipment, such as excavators and bulldozers, as well as in many industrial machines, such as presses and cranes.

Pneumatic devices use compressed air to transmit and control power. Air is compressed by a pump or compressor and then directed through a system of valves and actuators to perform work, such as powering a tool or controlling the movement of a machine. Pneumatic systems are commonly used in manufacturing and assembly operations, as well as in a variety of industrial applications, such as material handling and packaging.