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長(chang)途(tu)對稱(cheng)通(tong)信電纜由不同數(shu)量和不同絕(jue)(jue)(jue)(jue)緣(yuan)(yuan)(yuan)結構的四(si)(si)(si)線組構成。四(si)(si)(si)線組的常用(yong)形式為(wei)星絞(jiao)組，也有(you)(you)的采用(yong)復(fu)對絞(jiao)形式（圖2）。絕(jue)(jue)(jue)(jue)緣(yuan)(yuan)(yuan)有(you)(you)紙帶(dai)絕(jue)(jue)(jue)(jue)緣(yuan)(yuan)(yuan)、紙-繩(sheng)（紙帶(dai)和紙繩(sheng)）絕(jue)(jue)(jue)(jue)緣(yuan)(yuan)(yuan)、聚(ju)乙烯(xi)繩(sheng)-帶(dai)絕(jue)(jue)(jue)(jue)緣(yuan)(yuan)(yuan)、聚(ju)苯(ben)(ben)乙烯(xi)繩(sheng)－帶(dai)絕(jue)(jue)(jue)(jue)緣(yuan)(yuan)(yuan)和泡沫(mo)聚(ju)乙烯(xi)絕(jue)(jue)(jue)(jue)緣(yuan)(yuan)(yuan)等(deng)多種。高(gao)頻長(chang)途(tu)對稱(cheng)通(tong)信電纜傳輸頻率高(gao)，所以對電纜的結構性能(neng)要求較(jiao)高(gao)。一般(ban)采用(yong)繩(sheng)－帶(dai)絕(jue)(jue)(jue)(jue)緣(yuan)(yuan)(yuan)的星絞(jiao)四(si)(si)(si)線組結構。絕(jue)(jue)(jue)(jue)緣(yuan)(yuan)(yuan)材(cai)料常用(yong)聚(ju)苯(ben)(ben)乙烯(xi)、聚(ju)乙烯(xi)。紙帶(dai)紙繩(sheng)絕(jue)(jue)(jue)(jue)緣(yuan)(yuan)(yuan)一般(ban)用(yong)于252千赫以下(xia)的低頻對稱(cheng)通(tong)信電纜。

電(dian)(dian)(dian)(dian)(dian)(dian)話(hua)(hua)(hua)(hua)(hua)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)是用(yong)于(yu)(yu)(yu)市內、近郊和(he)工(gong)礦企業等(deng)較(jiao)小范圍的(de)區(qu)域電(dian)(dian)(dian)(dian)(dian)(dian)話(hua)(hua)(hua)(hua)(hua)連接的(de)對(dui)(dui)(dui)(dui)(dui)(dui)稱通(tong)信電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)，常稱市內電(dian)(dian)(dian)(dian)(dian)(dian)話(hua)(hua)(hua)(hua)(hua)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)。其(qi)主要(yao)特點為(wei)(wei)對(dui)(dui)(dui)(dui)(dui)(dui)數多(duo)(duo)（最多(duo)(duo)可(ke)(ke)達數千對(dui)(dui)(dui)(dui)(dui)(dui)，一(yi)(yi)般為(wei)(wei)數百(bai)或數十對(dui)(dui)(dui)(dui)(dui)(dui)）。由于(yu)(yu)(yu)使用(yong)頻(pin)率(lv)低，通(tong)信距離近，因此線(xian)(xian)徑較(jiao)長途(tu)通(tong)信電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)細，一(yi)(yi)般為(wei)(wei)0.5毫米。電(dian)(dian)(dian)(dian)(dian)(dian)話(hua)(hua)(hua)(hua)(hua)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)的(de)線(xian)(xian)組(zu)結構有(you)(you)對(dui)(dui)(dui)(dui)(dui)(dui)絞(jiao)(jiao)(jiao)(jiao)組(zu)、星絞(jiao)(jiao)(jiao)(jiao)組(zu)和(he)復(fu)對(dui)(dui)(dui)(dui)(dui)(dui)絞(jiao)(jiao)(jiao)(jiao)組(zu)3種。按(an)其(qi)線(xian)(xian)心(xin)(xin)(xin)絕緣(yuan)(yuan)(yuan)和(he)護層材料可(ke)(ke)分(fen)為(wei)(wei)紙(zhi)絕緣(yuan)(yuan)(yuan)鉛護套(tao)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)、聚乙烯絕緣(yuan)(yuan)(yuan)組(zu)合(he)護層電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)、油膏(gao)充填防(fang)水電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)、全塑電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)等(deng)。　電(dian)(dian)(dian)(dian)(dian)(dian)話(hua)(hua)(hua)(hua)(hua)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)中二根絕緣(yuan)(yuan)(yuan)導(dao)線(xian)(xian)心(xin)(xin)(xin)按(an)一(yi)(yi)定節距絞(jiao)(jiao)(jiao)(jiao)合(he)成對(dui)(dui)(dui)(dui)(dui)(dui)構成一(yi)(yi)個(ge)絕緣(yuan)(yuan)(yuan)線(xian)(xian)對(dui)(dui)(dui)(dui)(dui)(dui)。線(xian)(xian)對(dui)(dui)(dui)(dui)(dui)(dui)中二根絕緣(yuan)(yuan)(yuan)導(dao)線(xian)(xian)心(xin)(xin)(xin)的(de)顏色(se)不(bu)同(tong)（一(yi)(yi)般為(wei)(wei)紅(hong)色(se)和(he)白色(se)），以便(bian)接線(xian)(xian)時區(qu)分(fen)。電(dian)(dian)(dian)(dian)(dian)(dian)話(hua)(hua)(hua)(hua)(hua)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)的(de)纜(lan)(lan)(lan)(lan)(lan)(lan)心(xin)(xin)(xin)結構一(yi)(yi)般分(fen)為(wei)(wei)同(tong)心(xin)(xin)(xin)式(shi)和(he)單(dan)位式(shi)兩種（圖3）。同(tong)一(yi)(yi)層中相(xiang)鄰線(xian)(xian)對(dui)(dui)(dui)(dui)(dui)(dui)的(de)絞(jiao)(jiao)(jiao)(jiao)合(he)節距應不(bu)相(xiang)同(tong)，以減小通(tong)話(hua)(hua)(hua)(hua)(hua)時的(de)相(xiang)互影響。在(zai)每(mei)一(yi)(yi)層中都設有(you)(you)一(yi)(yi)個(ge)標(biao)志對(dui)(dui)(dui)(dui)(dui)(dui)（分(fen)別為(wei)(wei)藍色(se)和(he)白色(se)），便(bian)于(yu)(yu)(yu)接線(xian)(xian)時辨認。在(zai)80對(dui)(dui)(dui)(dui)(dui)(dui)以上(shang)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)中往往置(zhi)有(you)(you)預備線(xian)(xian)對(dui)(dui)(dui)(dui)(dui)(dui)以替換不(bu)合(he)格線(xian)(xian)對(dui)(dui)(dui)(dui)(dui)(dui)。單(dan)位式(shi)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)以50對(dui)(dui)(dui)(dui)(dui)(dui)或100對(dui)(dui)(dui)(dui)(dui)(dui)及相(xiang)應的(de)預備對(dui)(dui)(dui)(dui)(dui)(dui)絞(jiao)(jiao)(jiao)(jiao)合(he)成一(yi)(yi)個(ge)基(ji)本(ben)(ben)單(dan)位，再由若干個(ge)基(ji)本(ben)(ben)單(dan)位絞(jiao)(jiao)(jiao)(jiao)合(he)成電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)心(xin)(xin)(xin)。經干燥(zao)后擠壓(ya)上(shang)護套(tao)制(zhi)成電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)（見圖）。

架(jia)空敷設的電話電纜需用自(zi)承式(shi)，由鋼索承受整個(ge)電纜的重力。20世紀60年(nian)代以(yi)來，研(yan)制(zhi)出(chu)在塑料(liao)電纜中填(tian)充油膏以(yi)防止潮氣和水分(fen)的防水型電纜。

為(wei)了提高通信(xin)電纜的(de)防潮性、穩定(ding)性，20世紀(ji)70年代以(yi)來，在市內電話電纜中(zhong)廣泛采用綜合(he)型電纜護(hu)(hu)層(ceng)(ceng)(ceng)(ceng)。其(qi)基(ji)本類型有(you)3種。①Alpeth：纜心(xin)外(wai)(wai)擠壓(ya)一層(ceng)(ceng)(ceng)(ceng)聚(ju)(ju)乙(yi)烯(xi)(xi)護(hu)(hu)層(ceng)(ceng)(ceng)(ceng)，再(zai)搭接(jie)地縱(zong)向包(bao)裹0.2毫米皺(zhou)紋(wen)(wen)鋁帶(dai)，充以(yi)聚(ju)(ju)異丁烯(xi)(xi)絕緣復合(he)物后外(wai)(wai)敷(fu)一層(ceng)(ceng)(ceng)(ceng)熱塑性膠(jiao)粘(zhan)(zhan)層(ceng)(ceng)(ceng)(ceng)，最外(wai)(wai)面擠壓(ya)一層(ceng)(ceng)(ceng)(ceng)聚(ju)(ju)乙(yi)烯(xi)(xi)護(hu)(hu)套。②Stalpeth：皺(zhou)紋(wen)(wen)鋁帶(dai)外(wai)(wai)縱(zong)包(bao)一層(ceng)(ceng)(ceng)(ceng)皺(zhou)紋(wen)(wen)鋼帶(dai)，外(wai)(wai)覆一層(ceng)(ceng)(ceng)(ceng)熱塑性材(cai)料，最外(wai)(wai)層(ceng)(ceng)(ceng)(ceng)再(zai)擠壓(ya)一層(ceng)(ceng)(ceng)(ceng)聚(ju)(ju)乙(yi)烯(xi)(xi)護(hu)(hu)套。③Lepeth：纜心(xin)上包(bao)覆一層(ceng)(ceng)(ceng)(ceng)聚(ju)(ju)乙(yi)烯(xi)(xi)護(hu)(hu)套，其(qi)外(wai)(wai)敷(fu)一層(ceng)(ceng)(ceng)(ceng)粘(zhan)(zhan)性熱塑性材(cai)料，最外(wai)(wai)面擠壓(ya)一層(ceng)(ceng)(ceng)(ceng)鉛管(guan)。