Electrical device that has a fast response time and is used as a voltage surge limiter. The varistor is placed parallel to the circuit to protect sensitive components and absorb all peaks greater than its rated voltage. The MOV only suppresses transient peaks, and, if subjected to a constant high voltage, it burns. In this case, it is recommended to use the TMOVs, which include a thermal fuse. The capacity of these components is low, so they are suitable for the protection of circuits in digital switching.