This publication also bears a QC number. This number, QC 680100 is the specification number in the IEC Quality Assessment System for Electronic Components (IECQ). Applies to quartz crystal units manufactured as custom built products or as standard catalogue items and whose quality is assessed on the basis of capability approval. Prescribes the preferred ratings and characteristics, with the appropriate tests and measuring methods contained in the generic specification IEC 1178 1 and gives general performance requirements to be used in detail specifications for quartz crystal units.