Thinklabs One provides several frequency filters through which you can amplify different body sounds, for example,  a lower frequency filter for heart sounds (Bell) or a higher frequency filter for lung sounds (Diaphragm). The Thinklabs One filter appears as two LEDs on the frequency scale (in Hertz) as shown in the image to the left. 

Lower frequencies appear on the left side of the scale (Bell), and higher frequencies on the right (Diaphragm). When all LEDs on the frequency scale are illuminated, the full bandwidth filter is selected, which means no filter is used. This setting is highly useful for special use cases such as research applications. Additionally, you can set "favorite" filters to easily switch between Bell and Diaphragm. For more information, see How do I set favorite frequency filters?