Pneumatics is the use of pressurized gas to affect mechanical motion.
people
it compresses and expands gas so i would say pneumatics but not in the normal sense
I'll ignore the horrible way the question was asked.. Pneumatics use the flow of pressurised gas to transmit motion.
In a nutshell, pneumatics is a means whereby signals and energy are transmitted, controlled and distributed using pressurized air as the medium. Pneumatics can be effectively combined with other technologies through the use of sensors, transducers and microprocessors
pneumatics
oil is slightly compressible 0.5 % at 70 bar. but air is compressible. so to get the required pressure pneumatics require more energy source than hydraulics also there are some limitations for pneumatics in terms of force.
The Boeing 777 use the Pneumatics system.
A time activated switch could use pneumatics or an resistor capacitor circuit.
Hydraulics is the use of liquids to transmit power. Pneumatics is the use of gases (usually air) to transmit power.
Hydraulics use liquids as the working fluid, pneumatics use gases as the working fluid.
Pneumatics have the advantage over Hydraulics in that they are clean, require lower maintenance and respond quicker. When the application does not require that much force, pneumatics will do the job. Furthermore: the force needed for train doors should not be that large. It should only open and close the doors but not crush people that manage to get stuck in between