(Incase you are aware of computer lingo, we shouldn't really be using the term VGA, as VGA is actually a definition of the resolution -VGA = 640x480, XGA=1024x768, but it is often used anyway when talking around this subject)

Almost all video projectors will be able to take various signals, S-Video, Composite Video, and VGA (sometimes labeled RGB). The image opposite is the connection panel of a Video Projector - this o­ne has the option of connecting 2 computers, as well as an S-Video and composite video source. - I expect yours is simular.

Resolution
There are different resolutions you can send to video projectors. Resolution is the number of pixels that make up the image. The higher the resolution, the higher the number of pixels there are o­n the screen - this equates to a higher quality image. Composite video (and S-Video) is 720x576 pixels, and the various resolutions for RGB is:

VGA 640 x 480
SVGA 800 x 600
XGA 1024 x 768
SXGA 1280 x 1024
UXGA 1600 x 1200

Typically you'll be sending 800x600 or 1024x768 to the projector. (Check your projector specifications for the 'native' resolution of your model.)

Line Lengths
A standard VGA-type signal will normally travel around 15 metres down good quality cables before any drop-off may be seen. The signal might go considerably further than 15 metres, but the picture will deteriorate until the 'cliff-effect' is experienced, at which point there will be complete signal loss. The point at which the cliff-effect comes into play is variable, dependant o­n such things as temperature, relative humidity, the path the cable-run is to take, it's proximity to high voltage devices, etc. In other words, it is an inexact science. The image to the left is a photo of a computer screen with a 65 metre cable. The quality isn't that bad, but you can see the 'streaking' (Click o­n the image for a larger view)

So... if you're needing longer cable runs, then something needs to be done to ensure the signal is strong enough to get to the projector without a loss in quality! When you're setting up a system you may find that the signal is fine, however if it's not, then a 'Line Amplifier' will be required (pictured). A Line Amplifier will increase the signal strength o­n long cable runs. The device pictured is a line amplifier, and retails for around £120.

If you are needing to go over say 70-100 metres, then VGA probably won't give you the best results. In these cases, you can use products that convert the VGA signal to be run over CAT5/Twisted Pair cabling. (CAT5 cabling, is extensivly used in office networks.) These devices will allow the VGA signals to be run over long distances.

Multiple Projectors
In some buildings you'll be wanting to run more than just o­ne projector, in these cases you'll need a 'Distribution Amplifier' (Pictured). A Distribution Amplifier will take a single input (from the computer) and offer you multiple outputs. - The o­ne pictured has o­ne in, and 4 outs - Therefore allowing 4 video projectors to be run, this retails for about £130. You still may need a line amplifier if you are running long cables - maybe o­ne line amplifier for each of the outputs o­n the distribution amplifier.

Video overlay
Now you've got your projector(s) working and sending a VGA signal to them, you will now be thinking about how you can play a DVD, or send a camera feed to the projectors. There are 2 ways to do this:

• Use seperate cable runs from the DVD player to the projector o­n the composite source. This has the disadvantage of having to manually re-select the source o­n the video projector, which can be distracting to the congregation.
  
• Use a video capture card
  You'll loose a little of the quality, but it'll get made up in that it is very flexible, and will mean you can overlay the words o­n the video. See the Video Overlay page.