a. **Temperature control**

Within the furnace (**Figure 9a**), the thermometric transducer T is installed that transmits information of the temperature to the AB adjusting block.

In comparator C, a tension proportional to the desired value of the temperature θd, determined on the basis of the program imposed by technological process and controlled by the block of desired values BVD, is compared with a tension proportional to the real value of the temperature within furnace θr.

If θ<sup>r</sup> < θd, on–off regulator RBP is transmitting the closing command to adjusting block (connection switch to the power supply), and the furnace is absorbing power P. If θ<sup>r</sup> > θd, cutting-out command of the switch is transmitted.

The adjustment made with a dead zone Δθ is given by the regulator's characteristic (**Figure 9b**).
