| 
 A 
 | 
Organization of the work of ITU-T | 
| 
 D 
 | 
Tariff and accounting principles and international telecommunication/ICT economic and policy issues | 
| 
 E 
 | 
Overall network operation, telephone service, service operation and human factors | 
| 
 F 
 | 
Non-telephone telecommunication services | 
| 
 G 
 | 
Transmission systems and media, digital systems and networks | 
| 
 H 
 | 
Audiovisual and multimedia systems | 
| 
 I 
 | 
Integrated services digital network | 
| 
 J 
 | 
Cable networks and transmission of television, sound programme and other multimedia signals | 
| 
 K 
 | 
Protection against interference | 
| 
 L 
 | 
Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | 
| 
 M 
 | 
Telecommunication management, including TMN and network maintenance | 
| 
 N 
 | 
Maintenance: international sound programme and television transmission circuits | 
| 
 O 
 | 
Specifications of measuring equipment | 
| 
 P 
 | 
Telephone transmission quality, telephone installations, local line networks | 
| 
 Q 
 | 
Switching and signalling, and associated measurements and tests | 
| 
 R 
 | 
Telegraph transmission | 
| 
 S 
 | 
Telegraph services terminal equipment | 
| 
 T 
 | 
Terminals for telematic services | 
| 
 U 
 | 
Telegraph switching | 
| 
 V 
 | 
Data communication over the telephone network | 
| 
 X 
 | 
Data networks, open system communications and security | 
| 
 Y 
 | 
Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities | 
| 
 Z 
 | 
Languages and general software aspects for telecommunication systems |