I have a dataprojector, no signal

Then 'No signal' or 'unsupported signal' messages are usually because your display is set too high. To see if this is your issue, hoop it back up too your computer & set the computer to the basic VGA resolution. Assuming you are using windows, right click a blank area on the desktop, click 'properties' on the dropdown menu, click settings. Write down the numbers in the 'screen resolution' and 'color quality' boxes, then drag the 'screen resolution' all the way down to then 'less' side. Then change the 'color quality' to the lowest setting. Click apply, then answer yes (the display will look UGLY - don't worry!!) Now connect your computer back to your projector. If it works, then the resolution you use on your desktop monitor is not supported on your projector. Experiment with different resolutions to see which one looks best on your projector.

Note for Laptop users-- By default the VGA connector on your laptop is off. To turn it on, look for a blue symbol on one of your function (F1, F2, F3...) keys. It looks like an old TV with a line on both sides 'O' (F4 on HP) Press & hold the blue <fn> button (on the lower left of the keyboard, usually to the left of control <crtl>) and tap the bleu button you just found. Let go & give you