programming, the central unit will act on certain circuits related power signals picked up by the field elements concerned. [2] 2.5. Advantages and Disadvantages. Here, in this chapter, advantages and disadvantages will be defined. Let's start with advantages first. Next will be exposed the main of them: a) Energy saving: It is the biggest advantage, because when you can program all the devices you do not need to be spending all day. This is seen especially in the heating system