It's a camera on a stick or tripod and attached to your computer or projector. Many come with software for writing and recording the lesson on the computer but I am not sure how many teachers actually use those features. the recording part is great. The lesson can be saved for students who were absent. Or play the video when some one wakes up and asks what they missed :) Doc Cams are NOT just for doc(ument)s. ANYTHING you want to show you can show on the 8 foot screen. As long as you can point the camera at it! It is a camera after all! This includes a student doing an oral report or presentation, insects, simple machines, pottery... Document Cameras (many of the ones we have at our school anyway) cost $400 - $600. Yes they have come a lot in price. We also have a few $75 ones. We "Have" this Document camera, and this one.
Why are they so expensive?
They are great cameras and can zoom in close with a macro. They show crystals in rocks very well - BUT do you need that? The software is also very powerful for recording and editing your presentation. Have you ever used it?
What's my point?
In our new building we have two wall plates (hookups) that go to the projector. (Front and back of the classroom) If you do this you change your projector input from computer 1 to 2 or vice-versa.
Unplug your computer form the wall port that your computer is plugged in to and plug in your iPad (VGA/Dongle) cord into it. Assuming you can get to your wall plate!
Both your computer and iPad are plugged into this box and you simply switch from A to B to show one or the other on the screen.
Use an Apple TV or the Reflector application (via AirPlay) to display your iPad on the screen. While this seems like the best option since you can also move about the room it is totally relying on the wireless and has some lag time. See my other page about this.
Apps to use (click the icons)
Made by some dude who needed it. (Not a name brand) I have suggested this one for a few years now because it was the only one I could find! It works well.
Made by Belkin and has the backing of the backing of name branding. Also I think this app is a little more intuitive and easier to use.