Yamaha MDR-4 is a digital device that helps to minimize radio noise emissions and radio frequency interference. It comes with a cleaning cloth and user manual. The device should not be exposed to excessive force, extreme temperatures, high humidity or moisture, excessive dust or sand. If water or any liquid accidentally seeps into the MDR-4, or if it produces any abnormal odor or smoke, immediately turn off the power to the unit, unplug the power cord, and contact the Yamaha dealer from which you purchased the unit. Clean the outer case by wiping it only with a soft, dry cloth.