13. In exercising their functions under Part II of the Act, the Secretary of State and the Director shall ensure that operators of public telecommunications networks shall—
(a)publish and make readily available accurate and adequate technical specifications of all interfaces offered by them before services provided through such interfaces are made publicly available, and shall regularly publish any updated specifications, and
(b)provide in such publication the following information:
(i)sufficient details of technical interface specifications to permit the design of telecommunications terminal equipment capable of utilising all services provided through the corresponding interface;
(ii)details of changes in existing interface specifications, including information on network characteristics which are found to affect the correct operation of terminal equipment;
(iii)all the information necessary to allow manufacturers to carry out relevant tests, at their choice, for the essential requirements applicable to telecommunications terminal equipment.