We use piddle pads in addition to outdoors, but my boys let the humans know when they need to do 'big business.' (poop) They paw at us and get our attention first. It's difficult to explain, but we always know what they are trying to tell us.
If no one is in the room and the pad needs to be taken care of, Max has particular bark that we know means, "Hurry! We need service."
