A very simple instrucatble.
All you need is a DSL connection (wont work with dialup or cable from what I know) and this thing you can get at Radio Shack called the Fone Flasher. Basically you just plug it into a lamp and when a call comes it makes the lamp flash on and off. I got one for $1.50 at the clearance section.
Step 1: How To...
Just plug the jack into to a phone line anywhere in the house ,(You don't even have to plug it in to the power) and the dsl will be cut off. It happens because it doesn't have a dsl filter on it so it interferes with the connection and cuts it off. And best of all, all the cords to the modem are still attached so your siblings can't figure out why its not working! Have fun with it!