ITU-T N.21 PDF

General

This Recommendation gives limits in Tables 1/N.21 to 5/N.21 for the lining-up of an international soundprogramme circuit as defined in Recommendation N.1. These limits correspond to those for one audio section of the hypothetical reference circuit as defined in CCIR Recommendation 502 [1] for 5 kHz, 6.4 kHz, 7 kHz and 10 kHz sound-programme circuits, but correspond to two audio sections¹⁾ for 15 kHz type sound-programme circuits except for noise limits which correspond to one audio section.

It is recommended to use an automatic measuring equipment (see Recommendations O.31 [3], O.32 [4] and O.33 [5]). If no such equipment is available, measurements shall normally be restricted to loss/frequency distortion and weighted noise. For stereophonic pairs, the parameters Nos. 12, 13, 14 and 15 of Table 1/N.21 shall also be measured.

The limits for 15 kHz and 7 kHz circuits are applicable both for analogue and digital transmissions.

¹⁾ The limits derived for one audio to audio section for sound-programme circuits of 15 kHz nominal bandwidth calculated in accordance with CCIR Recommendation 605 [2] are not met by the technical specification of available equipment in use on the international network.