Any device with a primary function to condition the quality of commercial power received by a load. Sometimes also referred to as a line conditioner, a power conditioner typically provides protection against surges and spikes in power. Most power conditioners also provide basic EMI and RFI filtering by use of suppression circuits which keep such spurious signals out of audio circuits – provided it comes in on the AC line. Spikes and surges can damage your equipment. And while EMI (electromagnetic interference) and RFI (radio frequency interference) will not usually damage your equipment, they can cause unpredictable and unacceptable fleeting noises and – if strong enough – ruin a recording or performance.