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Some Extron switchers in classrooms have a picture in picture button this is often labeled PIP on the switcher insided the teacher station. When pressed this brings up a black box where the PIP would be displayed. Often times this button is easily pressed by knees on accident when people are standing in front of the switcher. If you see this black box on the projector screen look at the front of the Extron switcher and look for the button labeled PIP and press, this should turn off the picture in picture option and the black box should be gone.
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