PSTN in ITU-T standards
(www.itu.org)
nSeries
D Recommendations - General tariff principles
nSeries
E Recommendations - Overall network operation, telephone service, service operation and human
factorsnSeries G Recommendations - Transmission systems and media, digital
systems and networksnSeries I Recommendations - Integrated services digital network
(ISDN)nSeries
M Recommendations - Network maintenance: international transmission systems,
telephone circuits, telegraphy, facsimile, and leased circuits
ITU:
International Telecommunications Union