Blood pressure monitors use an inflatable air-bladder cuff and a listening device or pressure sensor to measure blood pressure in an artery. Blood pressure monitors consist of either manually inflated cuffs with a stethoscope for listening to arterial wall sounds or a blood pressure monitor that contains a pressure sensor for sensing arterial wall vibrations. The automatic blood pressure monitors consist of upper-arm and wrist models. Some blood pressure monitors can upload data to a computer for further analysis and tracking of measurements over time. This data transfer is usually done through a USB interface.