The APM-20 automatic phase switch is a device whose primary function is to maintain power continuity for single-phase loads in the event of a phase loss or a voltage drop below the specified value. The device's main advantage is a low relative voltage measurement error, not exceeding 1% even for highly distorted waveforms. This is achieved through the software implementation of a True RMS transducer. The APM-20 is powered by three phases: L1, L2, and L3, with L1 being the priority phase. The voltage switching threshold (180 V AC), switching time (150 ms), and voltage hysteresis (10 V AC) are factory-set and cannot be changed by the user. LEDs on the front panel provide a visual indication of each phase's parameters. The internal output contact system provides increased resistance to contact sticking and protects against phase-to-phase short circuits. The maximum output current should not exceed 16A for AC1 class loads. The APM-20 is designed for installation in distribution boards (TH-35). The housing is 2 modules wide.