The indicator of the position of the regulation switch of the power transformer PRS-31 is a replacement for classic indicators with resistors and an analog instrument. Compared to solutions with resistors, PRS-31 provides significantly higher reliability, given that it is much less sensitive to the quality of the contacts on the position sensor of the control switch and that there is no factor of aging and changes in the characteristics of the measuring elements. In addition, this device has additional alarm functions by means of which an irregular reading of the position of the control switch is signaled locally, on the display, and remotely, via the relay contact.