Both liquid and gas linear pumps utilize electromagnetism to apply force to a diaphragm or piston to positively displace air or pump liquid. Alternating current in electrical coils reverses the magnetic field induced around a magnetized rod at a rate determined by the supplied frequency. Movement of the diaphragm or piston attached to the end of the rod forces air through one-way valves. Linear diaphragm pumps are equipped with linear magnetic and vibrating armature motor types