EMI (Electro Magnetic Interference) refers to interference in audio equipment produced by the equipment or cabling picking up stray electromagnetic fields. This interference usually manifests itself as some type of hum, static, or buzz. Such electromagnetic fields are produced by fluorescent lights, power lines, computers, automobile ignition systems, television monitors, solid state lighting dimmers, AM and FM radio transmitters, and TV transmitters. Methods for controlling EMI include shielding of audio wiring and devices, grounding, elimination of ground loops, balancing of audio circuits, twisting of wires in balanced transmission lines, and isolation transformers among others. Completely eliminating EMI in a system ranges from easy to nearly impossible depending upon the equipment and the environment in question.