ARN-T 9 is freely programmable device which by: light indicators on front panel, LCD display and set of relay outputs monitors and regulates the voltage on transformer terminals. The controlled voltage value is measured by the voltage transformer of rated secondary value 100 V AC. The device compares the voltage value to expected value. The value of primary voltage is also presented on the display. The device supervises number of tap changer posistion by binary inputs. The tap changer position can be coded in BCD, binary or Gray code. Tap changer posistion as well as the voltage value are constantly sent to the supervision system. The tap changer is controlled by use of independent relay contacts. The position of tap changer can be coded in BCD, binary or Gray code and sent to other devices of the other value of the control voltage. There is also set of logical nodes to which any pair of contacts can be assigned. Example signals are: minimum and maximum position of tap changer or alarm of close to position close to maximum or minimum. The device offers also functionality of blocking by maximum or minimum voltage, overcurrent, tap changer motor overload. Lack of auxilliary voltage is indicated by the AL contact. All signals can be grouped as ALARM or Failure signals. 7 inch touch screen allows to monitor the operation of the device, preview of inputs and outputs, change the language, preview of real time, preview the event recorder data, preview the analog values.