To my understanding these units amplify the incoming signal with the help of an external power supply and push that stronger signal back out of the unit. Unfortunately it amplifies everything that is inbound, so if you have line noise due to damaged wiring or a really long cable run with substandard connections or incorrect sized wires, you will also amplify the garbage signals as well. Sometimes I have seen these units work well if they are placed more toward the leading edge of a long run rather than later when the line noise is too much. Hope that helps some.