ITU-T G.735-1988 工作在2048 kbit/s 并提供384 kbit/s 和/或64 kbit/s 同步数字接入的基群脉冲编码调制(PCM)复用设备的特性 Characteristics of primary PCM multiplex equipment operating at 2048 kbit/s and offering synchronous

pdf标准 ITU-T G.735-1988 工作在2048 kbit/s 并提供384 kbit/s 和/或64 kbit/s 同步数字接入的基群脉冲编码调制(PCM)复用设备的特性 Characteristics of primary PCM multiplex equipment operating at 2048 kbit/s and offering synchronous

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ITU-T G.735-1988 工作在2048 kbit/s 并提供384 kbit/s 和/或64 kbit/s 同步数字接入的基群脉冲编码调制(PCM)复用设备的特性 Characteristics of primary PCM multiplex equipment operating at 2048 kbit/s and offering synchronous 第 1 页 ITU-T G.735-1988 工作在2048 kbit/s 并提供384 kbit/s 和/或64 kbit/s 同步数字接入的基群脉冲编码调制(PCM)复用设备的特性 Characteristics of primary PCM multiplex equipment operating at 2048 kbit/s and offering synchronous 第 2 页 ITU-T G.735-1988 工作在2048 kbit/s 并提供384 kbit/s 和/或64 kbit/s 同步数字接入的基群脉冲编码调制(PCM)复用设备的特性 Characteristics of primary PCM multiplex equipment operating at 2048 kbit/s and offering synchronous 第 3 页 ITU-T G.735-1988 工作在2048 kbit/s 并提供384 kbit/s 和/或64 kbit/s 同步数字接入的基群脉冲编码调制(PCM)复用设备的特性 Characteristics of primary PCM multiplex equipment operating at 2048 kbit/s and offering synchronous 第 4 页 ITU-T G.735-1988 工作在2048 kbit/s 并提供384 kbit/s 和/或64 kbit/s 同步数字接入的基群脉冲编码调制(PCM)复用设备的特性 Characteristics of primary PCM multiplex equipment operating at 2048 kbit/s and offering synchronous 第 5 页
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INTERNATIONAL TELECOMMUNICATION UNION )45 4 ' TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU '%.%2!, !30%#43 /& $)')4!, 42!.3-)33)/. 3934%-3 4%2-).!, %15)0-%.43 #(!2!#4%2)34)#3 /& 02)-!29 0#-5,4)0,%8 %15)0-%.4 /0%2!4).' !4  KBITS !.$ /&&%2).' 39.#(2/./53 $)')4!, !##%33 !4  KBITS !.$/2  KBITS )45 4 Recommendation ' (Extract from the "LUE "OOK) NOTES 1 ITU-T Recommendation G.735 was published in Fascicle III.4 of the Blue Book. This file is an extract from the Blue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, the contents of the file are identical to the Blue Book version and copyright conditions remain unchanged (see below). 2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. © ITU 1988, 1993 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. Recommendation G.735 CHARACTERISTICS OF PRIMARY PCM MULTIPLEX EQUIPMENT OPERATING AT 2048 kbit/s AND OFFERING SYNCHRONOUS DIGITAL ACCESS AT 384 kbit/s AND/OR 64 kbit/s (former Recommendation G.737 of Volume III of the Yellow Book) This Recommendation gives the characteristics of a PCM multiplex equipment operating at 2048 kbit/s and providing one or several of the following internal digital access options: - bidirectional synchronous 64 kbit/s channels (see Figure l a/G.735); - unidirectional synchronous 384 kbit/s channels (see Figure 1b/G.735). The 384 kbit/s channel is based on the allocation of 6 x 64 kbit/s time slots, e.g. for setting up soundprogramme circuits according to Recommendations J.41 and J.42. Because these circuits are specified as unidirectional, the equipment for insertion/extraction has to be separated as shown in Figure 1b/G.735. 1 General characteristics 1.1 Fundamental characteristics for voice channel encoding The encoding law used is the A-law as specified in Recommendation G.711. The sampling rate, load capacity and the code are also specified in that Recommendation. The number of quantized values is 256. Note - The inversion of bits 2, 4, 6 and 8 is covered by the encoding law and is applicable only to voice channel time slots. 1.2 Bit rate The nominal bit rate is 2048 kbit/s. The tolerance on this rate is ± 50 parts per million (ppm). 1.3 Timing signal It should be possible to derive the transmit timing signal from any of the following: a) from the received 2048 kbit/s signal, b) from an external source at 2048 kHz (see § 5), c) from an internal oscillator. Note - The provision of a timing signal output, available for the purpose of synchronizing other equipments, is an option that might be required depending upon national synchronization arrangements. 1.4 Types of access: a) access for bidirectional synchronous 64 kbit/s channels (see Figure l a/G.735); b) access for unidirectional synchronous 384 kbit/s channels (see Figure 1b/G.735). Note - The synchronous insertion of a digital sound programme signal into a 384 kbit/s channel requires the internal regeneration of a timing signal T synchronized by the 2048 kbit/s signal I 1. The timing signal is used for Fascicle III.4 - Rec. G.735 1 synchronizing the sampling frequency of the analogue/digital converters producing the digital sound programme signal. FIGURE 1/G.735 PCM multiplex equipment operating it 2048 kbit/s and offering access to digital sound-programme signals and/or to synchronous 64 kbit/s data channels 2 Frame structure and use of derived channel time slots 2.1 Frame structure of 2048 kbit/s signal Refer to § 2.3 of Recommendation G.704. Bit 1 of the frame should be used in accordance with § 2.3.3 of Recommendation G.704, i.e. for a CRC check bit procedure. 2.2 Use of derived channel time slots 2.2.1 Telephone channels It should be possible to assign channel time slots 1 to 15 and 17 to 31 to thirty telephone channels numbered from 1 to 30. 2.2.2 64 kbit/s access The number of accessible channel time slots should be at least four and the equipment shall allow access to any 2 Fascicle III.4 - Rec. G.735 of channel time slots 1 to 15 and 17 to 31. Note - Equipment exists which provides access to at least four channel time slots in the following order of priority: 6 - 22 - 14 - 30 - 2 - 18 - 10 - 26 - 4 - 20 - 12 - 28 - 8 - 24 - 5 - 21 - 13 - 29 - 1 - 17 - 9 - 25 - 3 - 19 - 11 - 27 - 7 23 - 15 - 31. 384 kbit/s access 2.2.3 The time slot allocation for digital channels with a bit rate at 384 kbit/s is given in Table 1/G.735. TABLE 1/G.735 384 kbit/s channels (Note 1) D

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