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<html> <head> <meta content="en-us" http-equiv="Content-Language"> <meta content="text/html; charset=UTF-8" http-equiv="Content-Type"> <link type="text/css" rel="stylesheet" href="../../../../../css/ccna.css"> <script src="../../../../../js/framesetHelper.js" language="JavaScript"></script><script language="JavaScript"> window.scrollTo(0,0); function newPage(pageID) { alert("COMMING SOON!!\nThis feature is currently in development."); } function launchMoreInfo(oid) { dash = oid.indexOf('-'); sub1 = oid.substring(0,dash); sub2 = oid.substring(dash+1); // this is an URL base on the // system that generated the static // download of the curriculum. httpref = "http://nomar.sdf.cisco.com/servlet/org.cli.delivery.rendering.servlet.MIServlet/Static=true,LMSID=DTUI,Engine=dynamic,Theme=cnamstheme,Style=ccna,Language=en,Version=2,RootID=knet-v214aCV47051/CHAPID=null/RLOID=null/RIOID=null/"; newref = httpref + sub1 +"/"+ sub2 +"/moreinfoframeset.html"; //alert("new newref :\n" + newref); window.open(newref,'MoreInfo','toolbar=no,status=yes,menubar=no,location=no,scrollbars=yes,height=442,width=756,left=20,top=20,resizable=yes') } function launchContentResource(contentID) { top.currentSupport = 0; 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eval('top.frames.main_frame.location.href="'+ContentRef+'referencecontroller_crf.html"'); chapter = "knet-v214aCH47509"; ch_dash = chapter.indexOf('-'); ch_sub1 = chapter.substring(0,ch_dash); ch_sub2 = chapter.substring(ch_dash+1); params = "CHAPID=" + chapter + "/RLOID=" + "knet-v214aRLO47802" + "/RIOID=" + "knet-v214aRIO123556"; returnRef = "../../../../../"+ params + "/"+ ch_sub1 +"/"+ ch_sub2 +"/pageframeset.html"; top.prevPage = returnRef; } function launchFile(filepath) { newWindow = window.open(filepath,"","top=70,left=120,width="+(screen.width*.50)+",height="+(screen.height*.50)+",resizable=yes,scrollbars=yes,toolbar=yes,menubar=yes,status=yes"); /* if (is.ie && filepath.lastIndexOf(".pdf") != -1) { pageTimer = setInterval("winLoadCheck()", 1000); } */ } function winLoadCheck() { if (newWindow.document.readyState == 'complete') { clearInterval(pageTimer); newWindow.location.reload(); } } // BrowserCheck Object // provides most commonly needed browser checking variables // 19990326 // Copyright (C) 1999 Dan Steinman // Distributed under the terms of the GNU Library General Public License // Available at http://www.dansteinman.com/dynapi/ function BrowserCheck() { var b = navigator.appName if (b=="Netscape") this.b = "ns" else if (b=="Microsoft Internet Explorer") this.b = "ie" else this.b = b this.v = parseInt(navigator.appVersion) this.ns = (this.b=="ns" && this.v>=4) this.ns4 = (this.b=="ns" && this.v==4) this.ns5 = (this.b=="ns" && this.v==5) this.ie = (this.b=="ie" && this.v>=4) this.ie4 = (navigator.userAgent.indexOf('MSIE 4')>0) this.ie5 = (navigator.appVersion.indexOf('MSIE 5.0')>0) this.ie55 = (navigator.appVersion.indexOf('MSIE 5.5')>0) if (this.ie5) this.v = 5 this.min = (this.ns||this.ie) } // automatically create the "is" object is = new BrowserCheck()</script> </head> <body onLoad="window.focus();" alink="#000000" vlink="#000000" link="#000000" bgcolor="#E7E7E7" background="../../../../../images/ccna/common/bg.gif"> <table width="100%" cellspacing="0" cellpadding="2" border="0"><tr> <td bgcolor="#000000"><img height="1" width="2" border="0" src="../../../../../images/ccna/common/transdot.gif"></td><td class="rlohdr"><img height="1" width="2" border="0" src="../../../../../images/ccna/common/transdot.gif"></td><td valign="top" class="rlohdr">9.3</td><td width="100%" class="rlohdr"> <table width="90%" cellpadding="0" cellspacing="0" border="0"> <tr> <td class="rlohdr">Basics of Cable Installation</td> </tr> </table> </td> </tr> <tr> <td bgcolor="#000000"><img height="1" width="2" border="0" src="../../../../../images/ccna/common/transdot.gif"></td><td class="riohdr"><img height="1" width="2" border="0" src="../../../../../images/ccna/common/transdot.gif"></td><td valign="top" class="riohdr">9.3.1</td><td width="100%" class="riohdr"> <table width="90%" cellpadding="0" cellspacing="0" border="0"> <tr> <td class="riohdr">Basics of installing UTP cable</td> </tr> </table> </td> </tr> <tr> <td colspan="4"> <table width="90%" cellspacing="0" cellpadding="0" border="0"> <tr> <td class="smtext"> <p> </p><table cellpadding="0" cellspacing="0" width="100%" border="0" xmlns:java="http://xml.apache.org/xslt/java"> <tr> <td width="100%"><img height="10" width="1" border="0" src="../../../../../images/ccna/common/transdot.gif"></td> </tr> <tr> <td width="100%"> <table bgcolor="#000000" bordercolor="#000000" cellspacing="0" bordercolorlight="#000000" width="100%" border="0"> <tr> <td width="100%"> <table bgcolor="#FFFFFF" cellspacing="0" cellpadding="2" width="100%" border="0"> <tr> <td valign="middle"><img height="22" width="22" border="0" src="../../../../../images/ccna/common/inotes.gif"></td><td valign="middle"><span class="cstitle">Instructor Note</span></td> </tr> <tr> <td valign="top"> </td><td valign="top"><span class="cstext"> <p>This target indicator presents the "Dos" and "Don'ts" of installing UTP cable. It is best to demonstrate the various correct and incorrect procedures so the students are clear on how to treat the cable.</p> </span></td> </tr> </table> </td> </tr> </table> </td> </tr> </table><p>To connect cables to jacks, follow these steps:</p><ol><li>Strip back only as much of the cable's jacket as is required to terminate the wires. The more wire exposed, the poorer the connection, and the greater the signal loss.<img border="0" src="../../../../../CHAPID=knet-v214aCH47509/RLOID=knet-v214aRLO47802/RIOID=knet-v214aRIO123556/knet/v214adataimage1/1.gif" width="12" height="12"></li><li>Make sure that the twists in each pair of wires are maintained as much as possible, to the point of termination. It is the twisting of the wires that produces the cancellation that is needed to prevent radio and electromagnetic interference. For CAT 4 UTP, the maximum amount of untwisted wire that is allowed is 25 mm. For CAT 5 UTP, the maximum amount of untwisted wire that is allowed is 13 mm.<img border="0" src="../../../../../CHAPID=knet-v214aCH47509/RLOID=knet-v214aRLO47802/RIOID=knet-v214aRIO123556/knet/v214adataimage2/2.gif" width="12" height="12"></li><li>When bending the cable in order to route it, be sure to maintain a bend radius that is four times the diameter of the cable. Never bend cable to the extent that it is less than a 90掳 angle.<img border="0" src="../../../../../CHAPID=knet-v214aCH47509/RLOID=knet-v214aRLO47802/RIOID=knet-v214aRIO123556/knet/v214adataimage3/3.gif" width="12" height="12"></li><li>Avoid stretching cable when handling it. If 11.3 kg of pull is exceeded, the wires inside the cable can untwist, and that can lead to interference and cross talk.</li><li>If multiple cables must run over the same path, use cable ties to cinch them together. Position the ties at random intervals, then tighten them carefully. Never tighten the ties too much, as that can damage the cables.</li><li>Minimize the twisting of the cable jackets.<img border="0" src="../../../../../CHAPID=knet-v214aCH47509/RLOID=knet-v214aRLO47802/RIOID=knet-v214aRIO123556/knet/v214adataimage4/4.gif" width="12" height="12"> If they are twisted too much, the jackets may tear. Never allow cables to be pinched or kinked. If this occurs, data throughput will be reduced, and the LAN will operate at less than optimal capacity.</li><li>Never be stingy when determining the amount of cable that will be needed for running cable. It is important to leave ample slack. Remember, a few feet of extra cable is a small price to pay to avoid having to redo a cable run because of problems caused by stretched cable. Most cable installers avoid this problem by leaving enough slack for the cable to reach the floor, and extend another 60-90 cm at both ends. Most installers follow the practice of leaving what is called a service coil, which is simply a couple of extra meters of cable left coiled up inside the ceiling, or in another out-of-the-way location.</li><li>When securing the cable, use appropriate and recommended techniques for using cable ties, cable support bars, wire management panels, and releasable Velcro straps. Never use a staple gun to position cables. Staples can pierce the jacket, causing loss of connection.</li></ol><p>As always, remember the do's <img border="0" src="../../../../../CHAPID=knet-v214aCH47509/RLOID=knet-v214aRLO47802/RIOID=knet-v214aRIO123556/knet/v214adataimage5/5.gif" width="12" height="12"> and don'ts <img border="0" src="../../../../../CHAPID=knet-v214aCH47509/RLOID=knet-v214aRLO47802/RIOID=knet-v214aRIO123556/knet/v214adataimage6/6.gif" width="12" height="12"> for installing cable.</p><table cellpadding="0" cellspacing="4" width="63%" border="0" xmlns:java="http://xml.apache.org/xslt/java"> <tr> <td valign="middle" width="8%"><img height="23" width="23" src="../../../../../images/ccna/common/icon2.gif"></td><td valign="middle" width="92%"><span class="cstitle">Web Links</span></td> </tr> <tr> <td valign="middle" width="8%"> </td><td valign="middle" width="92%"><span class="smtext"><a target="_blank" href="http://www.siemon.com/glossary/definitions.html">Cabling Glossary</a></span></td> </tr> </table></td> </tr> </table> </td> </tr></table> <p> </p> <table width="100%" cellspacing="0" cellpadding="2" border="0" valign="bottom"> <tr> <td></td> </tr> </table> </body></html>⌨️ 快捷键说明
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