Impedance matching is the electronics design practice of setting the input impedance (ZS) of an electrical load equal to the fixed output impedance (ZL) of the signal source to which it is ultimately connected, usually in order to maximize the power transfer and minimize reflections from the load. This only applies when both are linear devices. The concept of impedance matching was originally developed for electrical power, but can be applied to any other field where a form of energy (not just electrical) is transferred between a source and a load. Matching is obtained when ZL = ZS