ITU-T G 733-1993 CHARACTERISTICS OF PRIMARY PCM MULTIPLEX EQUIPMENT OPERATING AT 1544 kbit s《工作在1544kbit s的基群脉冲编码调制(PCM)复用设备的特性》.pdf
《ITU-T G 733-1993 CHARACTERISTICS OF PRIMARY PCM MULTIPLEX EQUIPMENT OPERATING AT 1544 kbit s《工作在1544kbit s的基群脉冲编码调制(PCM)复用设备的特性》.pdf》由会员分享,可在线阅读,更多相关《ITU-T G 733-1993 CHARACTERISTICS OF PRIMARY PCM MULTIPLEX EQUIPMENT OPERATING AT 1544 kbit s《工作在1544kbit s的基群脉冲编码调制(PCM)复用设备的特性》.pdf(6页珍藏版)》请在麦多课文档分享上搜索。
1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU%.%2!,G0G0!30%#43G0G0/ further amended)1 General characteristics1.1 Fundamental characteristicsThe encoding law used is the -law as specified in Recommendation G.711. The sampling rate, load capacityand the cod
2、e are also specified in that Recommendation.The number of quantized values is 255. Two character signals are reserved for zero value (11111111 and01111111).In some networks the all-0 character signal (00000000) is eliminated to avoid loss of timing information to thedigital line, resulting in 254 qu
3、antized values.1.2 Bit rateThe nominal bit rate is 1544 kbit/s. The tolerance on this rate is 50 parts per million (ppm).1.3 Timing signalIt should be possible to derive the transmitting timing signal of a PCM multiplex equipment from an internalsource, from the incoming digital signal and also from
4、 an external source.2 Frame structureRefer to 3.1.1 and 3.1.2 of Recommendation G.704 for frame structure and use of derived channel time slots.3 Loss and recovery of frame alignmentThe strategy for the loss and recovery of frame alignment should be according to Recommendation G.706, 2.1.4 Fault con
5、ditions and consequent actions4.1 Fault conditionsThe PCM multiplex equipment should detect the following conditions:4.1.1 Failure of power supply.4.1.2 Loss of incoming signals at 1544 kbit/s.4.1.3 Loss of frame alignment.4.1.4 Alarm indication received from the remote PCM multiplex equipment.2 Fas
6、cicle III.4 - Rec. G.7334.2 Consequent actionsFurther to the detection of a fault condition, appropriate actions should be taken as specified in Table 1/G.733.The consequent actions are as follows:4.2.1 A service alarm indication should be generated to signify that the service provided by the PCM mu
7、ltiplex is nolonger available. This indication should be forwarded to the switching and/or signalling equipment depending upon thearrangement provided.4.2.2 The service alarm described in 4.2.1 above should be used to automatically remove the associated circuitsfrom service and to restore them to se
8、rvice when frame alignment has been recovered.Note - The removal of the associated circuits described in 4.2.2 above should be done in such a way that thecircuits are not needlessly removed in the case of a brief isolated loss of frame alignment but are removed in the case ofa permanent or intermitt
9、ent loss of frame alignment.It is also important to minimize the impact of signalling errors which may occur during periods of loss of framealignment. These functions should be provided in the PCM multiplex equipment or in the switching/signallingequipment.4.2.3 A prompt maintenance alarm indication
10、 should be generated to signify that performance is below acceptablestandards and maintenance attention is required locally.4.2.4 An alarm indication to the remote end should be generated by either forcing bit 2 in every channel time slot tothe value 0 or by modifying the S-bit as described in 3.1.3
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