The LKM-09 power supply indicator module is designed to display the presence of supply voltage in each phase. It can also be used to protect electrical receivers from the effects of current exceeding the allowable value, limited through the use of fuses. The device operates excellently even in cases of protective measurements that exceed 25A. Damage to the fuse will interrupt the supply from the power voltage and will turn off the appropriate LED, making the absence of supply voltage in one phase immediately visible. This facilitates preliminary diagnosis of the installation's condition. After the elimination of any faults and the replacement of the fuse with a new one, the system returns to normal operation. It is important to remember that the maximum current protection should not exceed 6A. In this configuration, the device can additionally serve as protection for control-measuring equipment, for example for relay sections.