A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The reverse operation (converting DC to AC) is performed by an inverter.
The process is known as rectification, since it "straightens" the direction of current. Physically, rectifiers take a number of forms, including vacuum tube diodes, wet chemical cells, mercury-arc valves, stacks of copper and selenium oxide plates, semiconductor diodes, silicon-controlled rectifiers and other silicon-based semiconductor switches. Historically, even synchronous electromechanical switches and motor-generator sets have been used. Early radio receivers, called crystal radios, used a "cat's whisker" of fine wire pressing on a crystal of galena (lead sulfide) to serve as a point-contact rectifier or "crystal detector".
Rectifiers have many uses, but are often found serving as components of DC power supplies and high-voltage direct current power transmission systems. Rectification may serve in roles other than to generate direct current for use as a source of power. As noted, rectifiers can serve as detectors of radio signals.
Depending on the type of alternating current supply and the arrangement of the rectifier circuit, the output voltage may require additional smoothing to produce a uniform steady voltage. Many applications of rectifiers, such as power supplies for radio, television and computer equipment, require a steady constant DC voltage (as would be produced by a battery). In these applications the output of the rectifier is smoothed by an electronic filter, which may be a capacitor, choke, or set of capacitors, chokes and resistors, possibly followed by a voltage regulator to produce a steady voltage.
Harley-Davidson, Inc. (H-D, or simply Harley) is an American motorcycle manufacturer headquartered in Milwaukee, Wisconsin, United States. Founded in 1903, it is one of two major American motorcycle manufacturers to survive the Great Depression along with its historical rival, Indian Motorcycles. The company has survived numerous ownership arrangements, subsidiary arrangements, periods of poor economic health and product quality, and intense global competition to become one of the world's largest motorcycle manufacturers and an iconic brand widely known for its loyal following. There are owner clubs and events worldwide, as well as a company-sponsored, brand-focused museum.
Harley-Davidson is noted for a style of customization that gave rise to the chopper motorcycle style. The company traditionally marketed heavyweight, air-cooled cruiser motorcycles with engine displacements greater than 700 cc, but it has broadened its offerings to include more contemporary VRSC (2002) and middle-weight Street (2015) platforms.
Harley-Davidson manufactures its motorcycles at factories in York, Pennsylvania; Milwaukee, Wisconsin; Manaus, Brazil; Bawal, India; and Pluak Daeng, Thailand. The company markets its products worldwide, and also licenses and markets merchandise under the Harley-Davidson brand, among them apparel, home décor and ornaments, accessories, toys, scale models of its motorcycles, and video games based on its motorcycle line and the community.