Power supply is a reference to a source of electrical power. A device or system that supplies electrical or other types of energy to an output load or group of loads is called a power supply unit or PSU. The term is most commonly applied to electrical energy supplies, less often to a mechanical ones, and rarely to others.

Power supplies for electronic devices can be broadly divided into linear and switching power supplies. The linear supply is a relatively simple design that becomes increasingly bulky and heavy for high current devices; voltage regulation in a linear supply can result in low efficiency. A switched-mode supply of the same rating as a linear supply will be smaller, is usually more efficient, but will be more complex.

? Battery power supply: A battery is a type of linear power supply that offers benefits that traditional line-operated power supplies lack: mobility, portability, and reliability. A battery consists of multiple electrochemical cells connected to provide the voltage desired.

? Linear power supply: A home-made linear power supply used to power amateur radio equipment. An AC power linear power supply usually uses a transformer to convert the voltage from the wall outlet (mains) to different sources, usually a lower voltage. If it is used to produce DC, a rectifier is used. A capacitor is used to smooth the pulsating current from the rectifier.

? An AC/DC Power Supply converts AC power to DC Power. An AC-DC Power Supply is a device that converts one form of electrical power to another desired form and voltage. This typically involves converting 120 or 240 volts AC supplied by a utility company to a well-regulated lower DC voltage for electrical devices.

? A switched-mode power supply works on a different principle. AC mains input is directly rectified without the use of a transformer, to obtain a DC voltage. This voltage is then sliced into small pieces by a high-speed electronic switch. The size of these slices grows larger as power output requirements increase.

is also known as a circuit diagram wiring diagram or elementary diagram. It is a simplified conventional pictorial representation of an electrical circuit. It shows the components of the circuit as simplified standard symbols, and the power and signal connections between the devices. Arrangement of the components interconnections on the diagram does not correspond to their physical locations in the finished device.

Unlike a block diagram or layout diagram, a circuit diagram shows the actual wire connections being used. The diagram does not show the physical arrangement of components. A drawing meant to describe what the physical arrangement of the wires and the components they connect is called "artwork" or "layout" or the "physical design." On a circuit diagram, the symbols for components are labelled with a descriptor matching that on the list of parts. Circuit diagrams are used for the design, construction, and maintenance of electrical and electronic equipment. Circuit diagram symbols have differed from country to country and have changed over time, but are now to a large extent internationally standardized. Simple components often had symbols intended to represent some feature of the physical construction of the device.

A less common symbol is simply a series of peaks on one side of the line representing the conductor, rather than back-and-forth. Different symbols may be used depending on the discipline using the drawing; for example, lighting and power symbols used as part of architectural drawings may be different from symbols for devices used in electronics.