Networks are in various stages of evolution towards being all-digital. Thus, there will be instances where: connections will be routed utilizing all-digital components (end-to-end including the terminals); other connections will use all-digital network components and analogue access facilities; and still other connections will use portions of the network which are analogue while other network components may be digital. This Recommendation is intended to address each of these scenarios. Because the trend is towards digital, the masking benefits of significant channel noise for certain impairments found in analogue networks can no longer be assumed. As a result, the guidance provided in this Recommendation will reflect this new environment.