The 3M Advance Overhead Projectors offer an array of features that make them versatile companions for all meeting-room and classroom environments. One model comes with an incredible inverted-head design that lowers the overall height of the projector a full 5-1/2-inches, so everyone gets an unobstructed view of your presentation. Three projectors have a hush-quiet fan that gets rid of unwanted noise. Others comes with such innovations as a unique color-tuning dial that ensures images won't drop off or fade at the corners of the screen and a rack-and-pinion mechanism that keeps image after image sharply focused during presentations. There's even a practical lamp ejector that makes replacing bulbs a simple task, a lamp changer that easily switches to a spare lamp for uninterrupted meetings, and a device that disconnects power to the lamp when switching from one bulb to another to prevent untimely lamp failure.