The International Telecommunication Union Telecommunication Standardization Sector (ITU-T) prepub-lished new versions of the K.20, K.21, K.44, and K.45 resistibility recommendations in July 2003. These recommendations are in force and replace the 2000 issued versions, covered by an earlier article. This article is based on this pre-published material, but correcting some obvious errors (see Conclusions). The increased coverage of the new recommendations withdraws four other ITU-T Recommendations. Recommenda-tions K.15 on remote-feeding systems and line repeaters and K.17 on power-fed repeaters are both absorbed into K.45. Recommendation K.22 on ISDN T/S bus equipment is absorbed into K.21 and K.41 on internal interfaces at telecommunication centres is absorbed into K.20. Recommendation K.44 picks up the test circuits from the absorbed recommendations. This article provides an overview of testing ports connected to symmetric-pair cables. The basic document structure remains the same. Recommendation K.44 is the test-circuit standard. Recommendation K.20 covers equipment located at a telecommunications center (central office), K.21 covers equipment located at customer premises (subscribers), and K.45 covers access and trunk equipment. This article provides an overview of testing ports connected to symmetric-pair cables
展开▼
