The field of application of this Recommendation is found in Recommendation Q.500. The signals taken into consideration are passed through the following interfaces as described in Recommendations Q.5 11 and Q.5 12 and Figure UQ.55 1. Interface A is for primary rate digital signals at 2048 kbit/s or 1544 kbit/s. Interface B is for secondary rate digital signals at 8448 kbit/s or 6312 kbitk. Interface types V are for digital subscriber line access.
ITU-T Q.554 SPANISH-1996 history
1996ITU-T Q.554 SPANISH-1996 Transmission characteristics at digital interfaces of digital exchanges