资源描述：
《传输设备维护手册》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。
1、107传输专业维护手册第一章传输原理介绍第一节SDH信号的帧结构和复用步骤1.1.1SDH信号——STM-N的帧结构STM-N信号帧结构的安排应尽可能使支路低速信号在一帧内均匀地、有规律的分布。为什么呢？因为这样便于实现支路的同步复用、交叉连接（DXC）、分/插和交换，说到底就为了方便的从高速信号中直接上/下低速支路信号。鉴于此，ITU-T规定了STM-N的帧是以字节（8bit）为单位的矩形块状帧结构，如图1-1所示。图1-1STM-N帧结构图从上图看出STM-N的信号是9行×270×N列的帧结构。此处的N与STM-N的N相一致，取值范围：1，4，16，64……。表示此信号由N个STM
2、-1信号通过字节间插复用而成。由此可知，STM-1信号的帧结构是9行×270列的块状帧，由上图看出，当N个STM-1信号通过字节间插复用成STM-N信号时，仅仅是将STM-1信号的列按字节间插复用，行数恒定为9行。我们知道，信号在线路上传输时是一个bit一个bit6.2.6establishingconstructionsiteweldingsecondary,secondaryelectrodeconsistedofRodpiledup,weldingrodovens,incubators,thermometers,hygrometersandbackingofelectrodes,
3、receiving,paymentandrecoverysystem.Andpersonresponsibleforthesecondarydatabase.6.2.7constructionweldingmachines,grindingmachines,plasmacuttingmachinetoolexperienceisqualified.6.2.8weldingelectrodes,weldingwireselectioninlinewithnationalandindustrystandardsrequirements,weldingmaterialweldingmater
4、ialsqualitymanualshouldbeprovided,itschemicalcomposition,mechanicalpropertiesandotherindicatorsshouldconformtotherequirementsoftherelevantstandards,appearancemaynothavedefectssuchascorrosion,unqualifiedproductscannotbeused.6.2.9electrode,fluxdryingbeforeuseaccordingtotheregulations,andshouldbeke
5、ptdryduringuse,wiresshouldberemovedbeforeusingthesurfaceoil,rust,etc.Electrodesmustnotfalloff,norustspotsandobviouscracks.6.36.3.1electrodeelectrodeselectionandmanagementlisttrumpeterargonarcweldingelectrodearcweldingofsteel10#E4303J427H08Mn2SiA20#E4303J427H08Mn2SiAQ235-AE4303J422,H08Mn2SiA304E3
6、08A102H0Cr21Ni10316LE00-19A002H00Cr21Ni10321E347A137H0Cr21Ni10Ti15Cr...(2)thepurityofargoncarbonsteelandalloysteelpipeshallnotbelessthan99.9%.(3)theweldingfieldwind-proof,rain-proofmeasuresmustbetaken,whentherelativehumidityisgreaterthan90%,whenthewindspeedisgreaterthan2m/s,donotallowapplication
7、ofargonarcwelding,whenthewindspeedisgreaterthan8M/s,donotallowtheapplicationofarcwelding.Weldingshallnotbelessthan0℃ambienttemperature.(4)priortowelding,youshouldreviewthelipsize,meettherequirementsbeforethey107传输专业维护手册107传输
