A : Organization of the work of ITU-T
D : General tariff principles
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 : Construction, installation and protection of cables and other elements of outside plant
M : Telecommunication management, including TMN and network maintenance