共查询到20条相似文献,搜索用时 343 毫秒
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由于ADSL传输速率高,占用频带宽,加上在市话电缆线路中传输的各种非话业务信号(如PCM、基带Modem、SDSL / HDSL等信号)的串扰,开放ADSL线路之间的相互串音,电力线、工业电器、无线电信号等感应噪声等因素,在市话电缆中并不是所有的线对都能够开通ADSL业务。所以在开通ADSL时要对用户线进行确认和选择,以确保所需速率的ADSL业务的开通。在日常维护中如果发现ADSL传输质量下降或有故障,则需要查找影响该线路ADSL传输的原因,进而提出解决方案。这些都需要借助于ADSL线路测试仪表。 影响ADSL传输的信道参数有衰… 相似文献
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专用通信网的研究一般需要专用的仪器进行测试。介绍了信令测试仪的主要功能。通过对面向对象技术和脚本技术的研究,提出了基于脚本机制的信令测试仪的实现方法,并实际研制了CPC信令测试仪。CPC信令测试仪在多个专用通信网的研制过程中得到实践,验证了该方法。 相似文献
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Vanguard与RAD PCM作为现今华东空管局的核心传输设备,承担着传输VHF信号的重要任务,在工作中发现两种设备的E&M接口特性不尽相同,这使得二者互联产生问题。文章就话音信号的传输以及E&M信令的特点,分析了Vanguard和RAD使用E&M信令传输VHF话音信号的原理。通过测试各针脚的电平,试分析两个设备互联传输话音信号不能实现的原因。 相似文献
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1 七号信令系统信令链路几种非正常状态的操作 (1)LINK STATE为ACTING,其TRAFSTATE为NOTRF。 可能是以下的两种情况: 1)本端系统工作正常,问题在对方机房,与对方交换机房联系,让对方处理。 2)由PCM传输告警引起的,应及时通知传输机房处理。 (2)LINK STATE为OOS,其TRAFSTATE为NOTRF。 相似文献
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利用PCM传输线路的数据网包括同步数据复接器和数据交换机。本文以电子数据交换(EDS)系统的同步网所用的系统单元作为例子,论述了这些复接器和交换机的功能。 相似文献
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Performance improvement of the nearly instantaneous companding PCM (or block companding PCM) is discussed. A simplified algorithm is proposed. The design and performance of a channel bank adopting the proposed algorithm is described. The channel bank can transmit 44 voiceband signals on a standard T1 line. It provides commercially acceptable speech quality as well as sufficient transparency for voiceband data up to 4800 bits/s. 相似文献
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Generalizations of the simple alternate mark inversion (AMI) line code that provide enhanced immunity to additive noise as well as spectral shaping are considered. The first technique is the extension of balanced disparity methods to multilevel signaling alphabets. This is a small step beyond simple codes such as AMI that are used to transmit binary PCM over twisted-pair cables. An important feature of this method (and later methods) is the use of suboptimal decoders. The most sophisticated technique used was Tomlinson (1971) filtering, and here it was possible to require a spectral null in the line code spectrum with a certain minimum width, and to minimize line code power subject to this requirement. This technique is compared to methods introduced by Marcus and Siegel (1987) in magnetic recording that provide spectral nulls at rational multiples of the symbol frequency. Theoretical possibilities, rather than techniques proven superior for a particular application, are addressed 相似文献
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Crucial to the design of digital switching systems for local switching applications is the line circuit interface. It forms the boundary between the analog, 2-wire, subscriber loop, with its attendant environment hostile to low-voltage electronics, and the digital logic environment. ITT North's DSS uses a Quad Line Circuit (QLC) that provides the line circuit interface between four subscriber loops and two PCM multiplexed highways. The QLC contains per-line elements consisting of an electronic 2W/4W hybrid, transmit and receive PCM filters, a codec, two card-mounted relays, and distributed logic for various gating and clocking functions. In addition, there is digital logic common to all four lines for interfacing with redundant microprocessors common to 320 lines. Design of the QLC in a dynamic technology evolution is discussed, and several evolutions of the initial design are presented. 相似文献
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程玉林 《电子科学学刊(英文版)》1994,11(2):135-142
Proceeding from the specific characteristics of PAL television signals adopted in China this paper points out that if the fs = 2fsc of sub-Nyquist sampling and DPCM encoding is used for PAL complete signal and if the blanking time is utilized to transmit code of effective area, it is possible to transmit a color TV signal over PCM three-group channel. 相似文献