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長途對稱通信(xin)電(dian)纜由不同數量和不同絕(jue)(jue)(jue)緣(yuan)(yuan)(yuan)結(jie)構的四線組(zu)構成。四線組(zu)的常用(yong)形式為(wei)星(xing)絞(jiao)組(zu)，也有的采用(yong)復(fu)對絞(jiao)形式（圖2）。絕(jue)(jue)(jue)緣(yuan)(yuan)(yuan)有紙帶(dai)絕(jue)(jue)(jue)緣(yuan)(yuan)(yuan)、紙-繩(sheng)(sheng)(sheng)(sheng)（紙帶(dai)和紙繩(sheng)(sheng)(sheng)(sheng)）絕(jue)(jue)(jue)緣(yuan)(yuan)(yuan)、聚(ju)乙烯(xi)繩(sheng)(sheng)(sheng)(sheng)-帶(dai)絕(jue)(jue)(jue)緣(yuan)(yuan)(yuan)、聚(ju)苯乙烯(xi)繩(sheng)(sheng)(sheng)(sheng)－帶(dai)絕(jue)(jue)(jue)緣(yuan)(yuan)(yuan)和泡沫聚(ju)乙烯(xi)絕(jue)(jue)(jue)緣(yuan)(yuan)(yuan)等(deng)多(duo)種。高頻長途對稱通信(xin)電(dian)纜傳(chuan)輸(shu)頻率(lv)高，所(suo)以對電(dian)纜的結(jie)構性(xing)能要(yao)求(qiu)較(jiao)高。一般采用(yong)繩(sheng)(sheng)(sheng)(sheng)－帶(dai)絕(jue)(jue)(jue)緣(yuan)(yuan)(yuan)的星(xing)絞(jiao)四線組(zu)結(jie)構。絕(jue)(jue)(jue)緣(yuan)(yuan)(yuan)材料常用(yong)聚(ju)苯乙烯(xi)、聚(ju)乙烯(xi)。紙帶(dai)紙繩(sheng)(sheng)(sheng)(sheng)絕(jue)(jue)(jue)緣(yuan)(yuan)(yuan)一般用(yong)于252千赫以下的低(di)頻對稱通信(xin)電(dian)纜。

電(dian)(dian)(dian)(dian)(dian)話(hua)(hua)(hua)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)是用于(yu)(yu)市(shi)(shi)內、近郊和(he)工礦企業(ye)等較小(xiao)范圍的(de)區域電(dian)(dian)(dian)(dian)(dian)話(hua)(hua)(hua)連接的(de)對(dui)(dui)(dui)(dui)(dui)稱(cheng)通(tong)(tong)信(xin)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)，常稱(cheng)市(shi)(shi)內電(dian)(dian)(dian)(dian)(dian)話(hua)(hua)(hua)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)。其(qi)主要特點為(wei)對(dui)(dui)(dui)(dui)(dui)數(shu)多（最多可(ke)達數(shu)千對(dui)(dui)(dui)(dui)(dui)，一(yi)(yi)(yi)般(ban)為(wei)數(shu)百或數(shu)十對(dui)(dui)(dui)(dui)(dui)）。由(you)于(yu)(yu)使用頻率(lv)低，通(tong)(tong)信(xin)距離(li)近，因(yin)此線(xian)(xian)(xian)(xian)徑較長途通(tong)(tong)信(xin)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)細，一(yi)(yi)(yi)般(ban)為(wei)0.5毫米。電(dian)(dian)(dian)(dian)(dian)話(hua)(hua)(hua)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)的(de)線(xian)(xian)(xian)(xian)組(zu)結構有對(dui)(dui)(dui)(dui)(dui)絞(jiao)組(zu)、星絞(jiao)組(zu)和(he)復(fu)對(dui)(dui)(dui)(dui)(dui)絞(jiao)組(zu)3種。按其(qi)線(xian)(xian)(xian)(xian)心(xin)絕(jue)(jue)緣(yuan)(yuan)(yuan)和(he)護層(ceng)材料可(ke)分為(wei)紙(zhi)絕(jue)(jue)緣(yuan)(yuan)(yuan)鉛護套(tao)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)、聚(ju)乙(yi)烯絕(jue)(jue)緣(yuan)(yuan)(yuan)組(zu)合(he)(he)護層(ceng)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)、油膏(gao)充填防水電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)、全塑(su)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)等。　電(dian)(dian)(dian)(dian)(dian)話(hua)(hua)(hua)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)中(zhong)二根絕(jue)(jue)緣(yuan)(yuan)(yuan)導線(xian)(xian)(xian)(xian)心(xin)按一(yi)(yi)(yi)定節(jie)距絞(jiao)合(he)(he)成(cheng)(cheng)對(dui)(dui)(dui)(dui)(dui)構成(cheng)(cheng)一(yi)(yi)(yi)個絕(jue)(jue)緣(yuan)(yuan)(yuan)線(xian)(xian)(xian)(xian)對(dui)(dui)(dui)(dui)(dui)。線(xian)(xian)(xian)(xian)對(dui)(dui)(dui)(dui)(dui)中(zhong)二根絕(jue)(jue)緣(yuan)(yuan)(yuan)導線(xian)(xian)(xian)(xian)心(xin)的(de)顏色不同(tong)(tong)(tong)（一(yi)(yi)(yi)般(ban)為(wei)紅色和(he)白(bai)(bai)色），以(yi)便(bian)接線(xian)(xian)(xian)(xian)時區分。電(dian)(dian)(dian)(dian)(dian)話(hua)(hua)(hua)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)的(de)纜(lan)(lan)(lan)(lan)(lan)(lan)心(xin)結構一(yi)(yi)(yi)般(ban)分為(wei)同(tong)(tong)(tong)心(xin)式和(he)單(dan)位(wei)(wei)式兩(liang)種（圖(tu)3）。同(tong)(tong)(tong)一(yi)(yi)(yi)層(ceng)中(zhong)相(xiang)鄰線(xian)(xian)(xian)(xian)對(dui)(dui)(dui)(dui)(dui)的(de)絞(jiao)合(he)(he)節(jie)距應(ying)不相(xiang)同(tong)(tong)(tong)，以(yi)減小(xiao)通(tong)(tong)話(hua)(hua)(hua)時的(de)相(xiang)互影響(xiang)。在(zai)每一(yi)(yi)(yi)層(ceng)中(zhong)都設有一(yi)(yi)(yi)個標志對(dui)(dui)(dui)(dui)(dui)（分別為(wei)藍色和(he)白(bai)(bai)色），便(bian)于(yu)(yu)接線(xian)(xian)(xian)(xian)時辨認(ren)。在(zai)80對(dui)(dui)(dui)(dui)(dui)以(yi)上的(de)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)中(zhong)往(wang)往(wang)置有預備(bei)線(xian)(xian)(xian)(xian)對(dui)(dui)(dui)(dui)(dui)以(yi)替換不合(he)(he)格線(xian)(xian)(xian)(xian)對(dui)(dui)(dui)(dui)(dui)。單(dan)位(wei)(wei)式電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)以(yi)50對(dui)(dui)(dui)(dui)(dui)或100對(dui)(dui)(dui)(dui)(dui)及相(xiang)應(ying)的(de)預備(bei)對(dui)(dui)(dui)(dui)(dui)絞(jiao)合(he)(he)成(cheng)(cheng)一(yi)(yi)(yi)個基本單(dan)位(wei)(wei)，再(zai)由(you)若(ruo)干個基本單(dan)位(wei)(wei)絞(jiao)合(he)(he)成(cheng)(cheng)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)心(xin)。經干燥后擠壓上護套(tao)制成(cheng)(cheng)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)(lan)(lan)（見(jian)圖(tu)）。

架空敷設的電(dian)話電(dian)纜(lan)需用自承式(shi)，由鋼索承受整個(ge)電(dian)纜(lan)的重(zhong)力(li)。20世紀60年代(dai)以來，研制出在塑料電(dian)纜(lan)中填(tian)充油膏以防止潮氣(qi)和水(shui)分的防水(shui)型電(dian)纜(lan)。

為了提高通信電(dian)纜(lan)的(de)防潮性(xing)(xing)、穩(wen)定性(xing)(xing)，20世紀70年代以(yi)來，在市(shi)內電(dian)話電(dian)纜(lan)中廣泛(fan)采(cai)用綜合型電(dian)纜(lan)護(hu)層(ceng)(ceng)(ceng)。其基本類型有3種。①Alpeth：纜(lan)心外(wai)(wai)擠壓(ya)一(yi)(yi)層(ceng)(ceng)(ceng)聚(ju)乙(yi)烯護(hu)層(ceng)(ceng)(ceng)，再(zai)搭接地縱向包裹0.2毫(hao)米皺(zhou)(zhou)紋(wen)鋁帶，充以(yi)聚(ju)異丁烯絕緣(yuan)復合物后外(wai)(wai)敷一(yi)(yi)層(ceng)(ceng)(ceng)熱塑性(xing)(xing)膠粘層(ceng)(ceng)(ceng)，最(zui)外(wai)(wai)面擠壓(ya)一(yi)(yi)層(ceng)(ceng)(ceng)聚(ju)乙(yi)烯護(hu)套(tao)。②Stalpeth：皺(zhou)(zhou)紋(wen)鋁帶外(wai)(wai)縱包一(yi)(yi)層(ceng)(ceng)(ceng)皺(zhou)(zhou)紋(wen)鋼帶，外(wai)(wai)覆一(yi)(yi)層(ceng)(ceng)(ceng)熱塑性(xing)(xing)材(cai)料，最(zui)外(wai)(wai)層(ceng)(ceng)(ceng)再(zai)擠壓(ya)一(yi)(yi)層(ceng)(ceng)(ceng)聚(ju)乙(yi)烯護(hu)套(tao)。③Lepeth：纜(lan)心上(shang)包覆一(yi)(yi)層(ceng)(ceng)(ceng)聚(ju)乙(yi)烯護(hu)套(tao)，其外(wai)(wai)敷一(yi)(yi)層(ceng)(ceng)(ceng)粘性(xing)(xing)熱塑性(xing)(xing)材(cai)料，最(zui)外(wai)(wai)面擠壓(ya)一(yi)(yi)層(ceng)(ceng)(ceng)鉛管。