This part of IEC 60368 applies to piezoelectric filters as custom-built products or as standard catalogue items 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 60368-1, and gives the general performance requirements to be used in detail specifications for piezoelectric filters. The concept of preferred values is directly applicable to standard catalogue items, but does not necessarily apply to custom-built products.