Touch the touchpanel screen to wake it up.

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Press the UP arrow in PLUS sign as indicated near the top right corner of the touchpanel to turn up the volume Image Removed
Press the DOWN arrow in the top right corner of the touchpanel to turn up MINUS sign as indicated near the center right of the touch panel to turn down the volume

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Press the the MUTE AUDIO button  button to silence the audio. Press it again to restore the audio.

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Press the *BLANK PROJECTORSCREEN *button to blank the screen. Press it again to restore the picture.
Even though the class won't see anything on the screen, you will still be able to see the picture on the teaching console monitor.