This part of IEC 60679 applies to quartz crystal controlled oscillators as custom built products or as standard catalogue items and whose quality is assessed on the basis of capability approval. It prescribes the preferred ratings and characteristics, with appropriate tests and measuring methods contained in the generic specification, IEC 60679-1, and gives the general performance requirements to be used in detail specifications for quartz crystal controlled oscillators. The concept of preferred values is directly applicable to standard catalogue items but does not necessarily apply to custom built products.