Recognizing that the CCITT Recommendations on ISDN apply to public ISDNs and may apply to private ISDNs, there is a need to ensure smooth service interworking across public and private ISDNs such that the services provided are transparent to the user across the public and private network components. This Recommendation aims to provide general principles and guidelines for the interworking of public and private ISDNs. The following objectives are envisaged in the development of Recommendations on public/private ISDN interworking: 1) the provision of common compatible functionality to provide common ISDN services; 2) the provision of end-to-end (TE1-type) ISDN terminal connectivity as well as terminal interchangeability; 3) a common overall ISDN transmission plan.