RVL50 Basic version of RVL55 - no "PopCard" menu or extension modules. Direct replacement by RVL480 same dimensions and panel out-out. 
Info: Do not use the existing base as terminals are different - the 
Key data to replacement product: unit must be rewired. Bus communication between RVL50 and the 
Key data to replacement product: RVL400 controllers is not possible (e.g. outside temperature).