scope:

This standard applies to Adaptive Differential Pulse-Code Modulation (ADPCM) Telecommunications systems where the channel pulse rate is 32 kbit/s.

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This standard provides for line formats used in Bundle, Transition, and Robbed-Bit Signaling modes for transcoded channels comprising channel pulse rates of 32 kbit/s combined in a line format operating at a pulse rate of 1544 kbit/s.

Section 3 of American National Standard for Telecommunications - Digital Processing of Voice-Band Signals - Algorithms for 24-, 32-, and 40-kbit/s Adaptive Differential Pulse-Code Modulation (ADPCM), ANSI T1.303-1989, specifies the 24- and 32-kbit/s ADPCM algorithms. Therefore the low bit-rate voice (LBRV) terminals that use the Bundle and lmnsition signaling line formats shall comply with the 32-kbit/s algorithm and those terminals that use the Robbed-Bit signaling line format shall comply with the 24- and 32-kbit/s algorithms as described in that section.

This standard provides for interface specification defining bit formats and actions associated with transcoder interfaces that use these line formats.

Purpose and Application The 48channel transcoder provides for the conversion between two 24-channel 1544-kbit/s PCM streams (ports X and Y) and one 48-channel 1544-kbit/s ADPCM stream (port Z). In the 24channel 1544-kbit/s streams, the voice frequency signals are coded at 64 kbit/s according to the PCM p-law defined in CCITT Red Book Volume III, Recommendation G.711, Pulse Code Modulation (PCM) of Voice Frequencies. In the 48-channel 1544kbit/s stream, the voice frequency signals are coded using 4 bits per channel according to the ADPCM algorithm in ANSI T1.303-1989.

Figure 1 represents the nomenclature used for the three different signal ports X, Y, and Z.

This standard contains the interface requirements associated with the line formats for 44- to 48-channel transcoders and is divided into four parts: Section 2 provides a listing of referenced standards, Section 3, 4, and 5 describe the line formats for trandscoders using the Bundle Format, Transition Signalig, and Robbed-Bit Signaling, respectively. Seclection of a transcoder emplouing a partcular line format will be based upon the slpecific application needs.