How do I change audio and visual inputs in the classroom? Why is the sound not playing from the lectern computer in the classroom?   The audio/video switchbox pictured above is located in many classrooms across the campus and can usually be found above the computer in the lectern cabinet. This device allows you quickly change what is displayed on the digital projector and what sound played through the classroom speakers. Press one of the labeled input buttons less than 2 seconds to switch the video to a different input (ie. Doc Camera or Laptop). Press and hold one of the labeled input until it beeps to switch the video and audio input. (ie. Using a laptop to present a video with sound or switching audio & video back to the classroom computer). For general use, you would want to see the bright green and orange lights under the input button labeled “COMPUTER.” The orange light indicates which video source is selected. The green light indicates which audio source is selected. You may notice that dim orange and green lights always appear under the COMPUTER input. This is normal but the actual selected input lights should appear noticeably brighter.