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A slip ring (in electrical engineering terms) is a method of making an electrical connection through a rotating assembly. Slip rings, also called rotary electrical interfaces, rotating electrical connectors, collectors, swivels or electrical rotary joints, are commonly found in electrical generators for AC systems and alternators and in packaging machinery, cable reels, wind turbines.

A slip ring consists of a conductive circle or band mounted on a shaft and insulated from it. Electrical connections from the rotating part of the system, such as the rotor of a generator, are made to the ring. Fixed contacts or brushes run in contact with the ring, transferring electrical power or signals to the exterior, static part of the system.

This system is similar to the brushes and commutator found in many types of DC motors. While commutators are segmented, slip rings are continuous, and the terms are not to be used interchangeably. Slip rings can also be used where electrical power or signals need to be transferred to a rotating device, such as an aerodrome beacon, rotating tank, or radio telescope. Rotary transformers are often used instead of slip rings in high speed or low friction environments.

Mercury wetted slip rings, noted for their low resistance and stable connection use a different principle which replaces the sliding brush contact with a pool of liquid metal molecularly bonded to the contacts. During rotation the liquid metal maintains the electrical connection between the stationary and rotating contacts.

Notable manufacturers of slip rings include: Air Precision [1](Paris, France),LABEL SAS (France), Trolex Engineering (UK), Michigan Scientific Corp. (USA), Asian Tool (Taipei, Taiwan), Moog Components Group (USA), MORGAN-REKOFA, and Schleifring of Germany. Electro Miniatures of Moonachie, New Jersey and Airflyte Electronics of Bayone, New Jersey are also suppliers of all sizes of slip rings, mercury wetted rotating electrical connectors are manufactured by: Mercotac Inc.(USA), Meridian Laboratory (USA) http://meridianlab.com. ]