Maintenance of international telegraph, phototelegraph and leased circuits : maintenance of the international public telephone network: maintenance of maritime satellite and data transmission systems: recommendations M.800 - M.1375 / International Telecommunication Union
Maintenance of international sound-programme and television transmission circuits : series N recommendations / International Telecommunication Union
Telephone transmission quality : series P recommendations / International Telecommunication Union
General recommendations on telephone switching and signalling : functions and information flows for service in the ISDN: supplements: recommendations Q.1- Q.118 bis / International Telecommunication Union