The signaling, centralization and interlocking devices used in domestic mines operate at voltages from 12 to 250 volts - in the range of the low voltage scale. As the operating experience has shown, the reliability of signaling and blocking systems does not depend on the voltage at which these devices operate. Safety of operation of signaling and control systems, from the point of view of their maintenance, is in inverse dependence on the voltage value. But, taking into account that signalling and control systems are low-voltage stationary installations, the fulfillment of safety rules, which eliminate the possibility of accidents at high voltage values, during their operation does not cause significant difficulties. The main factor determining the optimality of the voltage value of signalling systems is the economic costs of power supply. In this case the most favorable voltage value will also be the optimal one for these specific conditions.