To ensure traceability to national standards, it is essential to maintain the reliability of calibration, in which a standard device is calibrated by a higher standard device, between national measurements and ones used at various locations such as factories and research institutes. In order to calibrate standard devices or to produce reference materials, specific skills and equipment are necessary, and also a quality system is essential to maintain such skills and equipment. Laboratories are accredited by the National Institute of Technology and Evaluation (NITE) when they meet such requirements and pass the examination conducted by NITE. Standard devices carried by accredited laboratories are called secondary measurement standards, and calibrated by primary measurement standards (or primary sub-measurement standards). Similarly, reference materials produced by them are called secondary reference materials, and calibrated by primary reference materials. This system is called "the Japan Calibration Service System" (JCSS). For further information, visit the JCSS web site.