Invisible fence? How big of an area?

Hey Great, I found it I have been looking for this thread for ages because I forgot to add something neat about an invisable fence............

You can use it inside too! I have a loop of it running under the kitchen counter and over the garbage/compost pail so the dogs dont do the help yourself to what you want thing in MY kitchen. You cant see the wire but you can sure hear when one forgets her/him self and goes for some tempting treat