IEC 60539-1:2022 is applicable to directly heated negative temperature coefficient thermistors, typically made from transition metal oxide materials with semiconducting properties. It establishes standard terms, inspection procedures and methods of test for use in sectional and detail specifications of electronic components for quality assessment or any other purpose. This edition includes the following significant technical changes with respect to the previous edition: Restructured completely to comply to ISO/IEC directives; categorization and reorganization of test methods into these categories; Annex X added for comparison to the previous edition; Some wordings, figures and references have been revised.