overhead projector: 1) Cool steel metal case and anti-static electricity 2) Streamline design, beautiful and elegant 3) Circular transformer, high efficiency and low energy consume 4) Low-noise cooling system 5) Convenient to store and packaging 6) Hi-low switch 7) 180 degree head rotation 8) Power shut off when top cover opened 9) Reliable and convenient folded spring pole and self-lock device