Article 55 Must-carry obligations Must-carry obligations may be imposed on undertakings providing electronic communications networks for the distribution of radio or television broadcasts to the public, where a significant number of users utilise the networks to receive radio and television broadcasts. Such obligations shall only be imposed where there are especially cogent reasons for so doing. Article 56 Conditional access systems Conditional access to digital television and radio services must satisfy rules set by PTA on the basis of obligations under the EEA Agreement. These provide, for instance, for the technical characteristics and obligations to grant access. Article 57 Standards in interactive television services PTA shall direct undertakings operating digital interactive television services for distribution to the public or selling enhanced digital television equipment to use an open application program interface (API) in accordance with obligations under the EEA Agreement. Article 58 Requirements for digital broadcasting on public electronic communications networks Public electronic communications networks established for the distribution of digital television services shall be capable of distributing wide-screen television services and programmes. Electronic communications undertakings which receive and distribute wide-screen television services or programmes shall maintain that wide-screen format. CHAPTER XII Electronic communications equipment Article 59 Electronic communications network equipment Equipment used in a public electronic communications network shall as a rule comply with technical standards in force in the EEA. PTA may, in special instances, prescribe the use of other standards or recommendations from the International Telecommunication Union. Technical characteristics of NTPs shall always be in accordance with standards. An electronic communications undertaking operating a public electronic communications network must publish information on technical characteristics of NTPs. The Minister of Communications may issue a Regulation1) on the detailed implementation of these 25/34