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長途對稱通(tong)信電纜由不(bu)(bu)同(tong)數量和不(bu)(bu)同(tong)絕(jue)緣(yuan)(yuan)(yuan)結構的(de)(de)四線組(zu)(zu)構成。四線組(zu)(zu)的(de)(de)常用形(xing)式為星絞(jiao)組(zu)(zu)，也(ye)有(you)的(de)(de)采用復對絞(jiao)形(xing)式（圖(tu)2）。絕(jue)緣(yuan)(yuan)(yuan)有(you)紙(zhi)(zhi)帶(dai)(dai)絕(jue)緣(yuan)(yuan)(yuan)、紙(zhi)(zhi)-繩(sheng)（紙(zhi)(zhi)帶(dai)(dai)和紙(zhi)(zhi)繩(sheng)）絕(jue)緣(yuan)(yuan)(yuan)、聚(ju)乙(yi)烯(xi)(xi)繩(sheng)-帶(dai)(dai)絕(jue)緣(yuan)(yuan)(yuan)、聚(ju)苯(ben)乙(yi)烯(xi)(xi)繩(sheng)－帶(dai)(dai)絕(jue)緣(yuan)(yuan)(yuan)和泡沫聚(ju)乙(yi)烯(xi)(xi)絕(jue)緣(yuan)(yuan)(yuan)等(deng)多種。高(gao)頻(pin)長途對稱通(tong)信電纜傳(chuan)輸頻(pin)率高(gao)，所以(yi)對電纜的(de)(de)結構性能要(yao)求較高(gao)。一(yi)般采用繩(sheng)－帶(dai)(dai)絕(jue)緣(yuan)(yuan)(yuan)的(de)(de)星絞(jiao)四線組(zu)(zu)結構。絕(jue)緣(yuan)(yuan)(yuan)材料常用聚(ju)苯(ben)乙(yi)烯(xi)(xi)、聚(ju)乙(yi)烯(xi)(xi)。紙(zhi)(zhi)帶(dai)(dai)紙(zhi)(zhi)繩(sheng)絕(jue)緣(yuan)(yuan)(yuan)一(yi)般用于(yu)252千赫以(yi)下的(de)(de)低頻(pin)對稱通(tong)信電纜。

電(dian)(dian)(dian)(dian)(dian)(dian)(dian)話(hua)(hua)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)是(shi)用于(yu)(yu)市(shi)內、近郊和(he)(he)工礦企業等較小(xiao)范圍(wei)的(de)(de)(de)區域電(dian)(dian)(dian)(dian)(dian)(dian)(dian)話(hua)(hua)連接(jie)(jie)的(de)(de)(de)對(dui)(dui)稱通(tong)信電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)，常稱市(shi)內電(dian)(dian)(dian)(dian)(dian)(dian)(dian)話(hua)(hua)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)。其主要特點(dian)為(wei)對(dui)(dui)數多(duo)（最多(duo)可達數千(qian)對(dui)(dui)，一(yi)(yi)般為(wei)數百或(huo)數十對(dui)(dui)）。由(you)于(yu)(yu)使用頻率低，通(tong)信距(ju)離(li)近，因此(ci)線(xian)徑較長(chang)途通(tong)信電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)細，一(yi)(yi)般為(wei)0.5毫(hao)米。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)話(hua)(hua)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)的(de)(de)(de)線(xian)組(zu)結構(gou)有(you)(you)對(dui)(dui)絞(jiao)(jiao)組(zu)、星絞(jiao)(jiao)組(zu)和(he)(he)復對(dui)(dui)絞(jiao)(jiao)組(zu)3種(zhong)(zhong)。按其線(xian)心(xin)絕(jue)(jue)緣(yuan)和(he)(he)護(hu)(hu)層(ceng)材料可分(fen)為(wei)紙(zhi)絕(jue)(jue)緣(yuan)鉛護(hu)(hu)套電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)、聚乙(yi)烯絕(jue)(jue)緣(yuan)組(zu)合(he)(he)(he)護(hu)(hu)層(ceng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)、油(you)膏充填(tian)防水電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)、全塑電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)等。　電(dian)(dian)(dian)(dian)(dian)(dian)(dian)話(hua)(hua)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)中(zhong)二(er)根絕(jue)(jue)緣(yuan)導(dao)線(xian)心(xin)按一(yi)(yi)定節(jie)距(ju)絞(jiao)(jiao)合(he)(he)(he)成(cheng)(cheng)對(dui)(dui)構(gou)成(cheng)(cheng)一(yi)(yi)個(ge)絕(jue)(jue)緣(yuan)線(xian)對(dui)(dui)。線(xian)對(dui)(dui)中(zhong)二(er)根絕(jue)(jue)緣(yuan)導(dao)線(xian)心(xin)的(de)(de)(de)顏色(se)不同（一(yi)(yi)般為(wei)紅色(se)和(he)(he)白色(se)），以(yi)(yi)(yi)便接(jie)(jie)線(xian)時區分(fen)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)話(hua)(hua)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)的(de)(de)(de)纜(lan)(lan)(lan)心(xin)結構(gou)一(yi)(yi)般分(fen)為(wei)同心(xin)式和(he)(he)單(dan)位式兩種(zhong)(zhong)（圖3）。同一(yi)(yi)層(ceng)中(zhong)相鄰線(xian)對(dui)(dui)的(de)(de)(de)絞(jiao)(jiao)合(he)(he)(he)節(jie)距(ju)應不相同，以(yi)(yi)(yi)減小(xiao)通(tong)話(hua)(hua)時的(de)(de)(de)相互影(ying)響(xiang)。在(zai)每一(yi)(yi)層(ceng)中(zhong)都設(she)有(you)(you)一(yi)(yi)個(ge)標志對(dui)(dui)（分(fen)別為(wei)藍(lan)色(se)和(he)(he)白色(se)），便于(yu)(yu)接(jie)(jie)線(xian)時辨認。在(zai)80對(dui)(dui)以(yi)(yi)(yi)上(shang)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)中(zhong)往往置(zhi)有(you)(you)預(yu)(yu)備線(xian)對(dui)(dui)以(yi)(yi)(yi)替換不合(he)(he)(he)格線(xian)對(dui)(dui)。單(dan)位式電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)以(yi)(yi)(yi)50對(dui)(dui)或(huo)100對(dui)(dui)及(ji)相應的(de)(de)(de)預(yu)(yu)備對(dui)(dui)絞(jiao)(jiao)合(he)(he)(he)成(cheng)(cheng)一(yi)(yi)個(ge)基(ji)本(ben)單(dan)位，再由(you)若干個(ge)基(ji)本(ben)單(dan)位絞(jiao)(jiao)合(he)(he)(he)成(cheng)(cheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)心(xin)。經(jing)干燥后擠壓上(shang)護(hu)(hu)套制成(cheng)(cheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)（見圖）。

架空敷設(she)的電話電纜需(xu)用(yong)自(zi)承(cheng)式，由鋼索承(cheng)受整個電纜的重力。20世紀(ji)60年代以來，研制出在塑(su)料電纜中填充油膏以防止(zhi)潮氣和水分的防水型電纜。

為了提高通(tong)信電(dian)纜(lan)的(de)防(fang)潮性(xing)、穩(wen)定性(xing)，20世紀70年代以來(lai)，在市內(nei)電(dian)話電(dian)纜(lan)中廣泛(fan)采用(yong)綜合型(xing)(xing)電(dian)纜(lan)護(hu)(hu)(hu)(hu)層(ceng)(ceng)(ceng)(ceng)。其基本類(lei)型(xing)(xing)有3種。①Alpeth：纜(lan)心外(wai)(wai)(wai)擠壓一(yi)(yi)(yi)層(ceng)(ceng)(ceng)(ceng)聚乙(yi)(yi)(yi)烯護(hu)(hu)(hu)(hu)層(ceng)(ceng)(ceng)(ceng)，再(zai)搭接(jie)地縱向包裹0.2毫米皺(zhou)紋鋁(lv)帶，充以聚異丁烯絕(jue)緣復合物后外(wai)(wai)(wai)敷(fu)一(yi)(yi)(yi)層(ceng)(ceng)(ceng)(ceng)熱(re)塑性(xing)膠粘(zhan)層(ceng)(ceng)(ceng)(ceng)，最外(wai)(wai)(wai)面擠壓一(yi)(yi)(yi)層(ceng)(ceng)(ceng)(ceng)聚乙(yi)(yi)(yi)烯護(hu)(hu)(hu)(hu)套(tao)。②Stalpeth：皺(zhou)紋鋁(lv)帶外(wai)(wai)(wai)縱包一(yi)(yi)(yi)層(ceng)(ceng)(ceng)(ceng)皺(zhou)紋鋼帶，外(wai)(wai)(wai)覆一(yi)(yi)(yi)層(ceng)(ceng)(ceng)(ceng)熱(re)塑性(xing)材料，最外(wai)(wai)(wai)層(ceng)(ceng)(ceng)(ceng)再(zai)擠壓一(yi)(yi)(yi)層(ceng)(ceng)(ceng)(ceng)聚乙(yi)(yi)(yi)烯護(hu)(hu)(hu)(hu)套(tao)。③Lepeth：纜(lan)心上包覆一(yi)(yi)(yi)層(ceng)(ceng)(ceng)(ceng)聚乙(yi)(yi)(yi)烯護(hu)(hu)(hu)(hu)套(tao)，其外(wai)(wai)(wai)敷(fu)一(yi)(yi)(yi)層(ceng)(ceng)(ceng)(ceng)粘(zhan)性(xing)熱(re)塑性(xing)材料，最外(wai)(wai)(wai)面擠壓一(yi)(yi)(yi)層(ceng)(ceng)(ceng)(ceng)鉛管。