ITU-T Recommendation E.180/Q.35 Series E: Overall network operation, telephone service, service operation and human factors… Series Q: Switching and signalling. International automatic… Technical characteristics of tones for the telephone service

ITU-T Recommendation E.177 Series E: Telephone network and ISDN. Operation, numbering, routing and mobile services – International operation – International routing plan. B-ISDN routing ITU-T Recommendation E.175 Telephone network and ISDN. Operation, numbering, routing and mobile service. Models for international network planning ITU-T Recommendation E.174 Telephone network and ISDN. Operation, numbering, routing and mobile service. Routing principles and guidance for universal personal telecommunications (UPT) ITU-T Recommendation E.181 Telephone network and ISDN. Operation, numbering, routing and mobile service. Customer recognition of foreign tones ITU-T Recommendation E.182 Series E: Overall network operation, telephone service, service operation and human factors. Operation, numbering, routing… Tones in national signalling systems. Application of tones and recorded announcements in telephone ... ITU-T Recommendation E.183 Series E: Overall network operation, telephone service, service operation and human factors. Operation, numbering, routing and mobile… Tones in national signalling systems. Guiding principles for telephone announcements