A Fader is a sliding variable resistor or potentiometer used to adjust signal levels on mixing consoles and control surfaces. Unlike rotary knobs, faders are designed for linear motion along a track, which provides immediate visual feedback regarding the relative levels of different audio tracks at a glance. This linear design also facilitates the manual operation of multiple channels at once, a crucial technique in live mixing and studio automation where blending several sources simultaneously is required. While they function electrically like any other volume pot, high-quality faders are engineered for smooth physical travel and often feature specific taper characteristics to match the sensitivity of the human ear to changes in loudness. In modern digital systems, faders are frequently motorized, allowing them to physically move in response to automation data recorded in a software, ensuring that the visual position of the fader always matches the actual volume level being reproduced.