This part of IEC 61643 presents a description, theory of operation, test characteristics, and application principles for MOVs, which are used for applications up to 1 000 V AC or 1 500 V DC in power line, or telecommunication, or signalling circuits. They are designed to protect apparatus or personnel, or both, from high transient voltages. This specification applies to MOVs having two electrodes and overvoltage protection components with or without disconnectors. This specification also does not apply to mountings and their effect on the MOV s characteristics. Characteristics given apply solely to the MOV mounted only in the ways described for the tests. This standard specifically discusses the zinc-oxide type of MOVs.