Hi. I have 4  Deco x55's that I have had for coming on three years. The main device is emitting a high pitched squeak and has a solid yellow light on it. I assume that it has failed and needs replacing. Am I best off buying another x55 or is there a newer version that could act as the main device and still be comaptible with the other x55's? I am assuming these will eventually need replacing so I am trying to plan for the future rather than just scrap the whole lot. Thanks in advance.