The encoding law used is the μ-law as specified in Recommendation G.711. The sampling rate, load capacity and the code are also specified in that Recommendation.
ITU-T G.733-1993 Referenced Document
ITU-T G.703 Physical/electrical characteristics of hierarchical digital interfaces*, 2016-03-31 Update
ITU-T G.704 Synchronous Frame Structures Used at 154463122048 8448 and 44 736 kbit/s Hierarchical Levels - Series G: Transmission Systems and Media Digital Systems and Networks Digital Transmission Systems - Terminal Equipments - General Study Group 15; 44 pp*, 1998-04-19 Update
ITU-T G.706 Frame Alignment and Cyclic Redundancy Check (CRC) Procedures Relating to Basic Frame Structures Defined in Recommendation G.704 (Study Group XVIII) 19 pp
ITU-T G.711 PULSE CODE MODULATION (PCM) OF VOICE FREQUENCIES
ITU-T G.712 Transmission performance characteristics of pulse code modulation channels = SERIES G: TRANSMISSION SYSTEMS AND MEDIA DIGITAL SYSTEMS AND NETWORKS - Digital terminal equipments - Coding of analogue signals by pulse code modulation*, 2024-04-19 Update
ITU-T G.733 CHARACTERISTICS OF PRIMARY PCM MULTIPLEX EQUIPMENT OPERATING AT 1544 kbit/s
ITU-T Q.275 6.5 Data Channel Failure Detection - Specifications of Signalling System No. 6 (Study Group XI) 1 pp
ITU-T G.733-1993 history
1993ITU-T G.733-1993 CHARACTERISTICS OF PRIMARY PCM MULTIPLEX EQUIPMENT OPERATING AT 1544 kbit/s