MEDO air pumps are manufactured in Japan and have been adapted from the medical industry. The air is pumped using a pair of teflon pistons (no diaphragms) into a reservoir in the base of the unit. This means it is possible to push through air from an airstone at greater depth without risk of damage to the components.
The Medo LA200 Linear-motor-driven Free Piston System (Pat.) has an internal piston inside the cylinder which is driven by an electro-magnet and spring system controlled by the alternating input current cycle. The piston thus forms a single combined structure of two usually different devices; motor and pump. The system is quiet and vibration free, and offers the advantages of easy maintenance and a long operating life.