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長(chang)途對稱通信電(dian)(dian)(dian)纜由(you)不同數量和(he)不同絕(jue)(jue)(jue)緣(yuan)結(jie)構的(de)四線組(zu)構成(cheng)。四線組(zu)的(de)常用(yong)(yong)形式為星絞(jiao)組(zu)，也(ye)有的(de)采用(yong)(yong)復對絞(jiao)形式（圖2）。絕(jue)(jue)(jue)緣(yuan)有紙(zhi)帶(dai)(dai)(dai)絕(jue)(jue)(jue)緣(yuan)、紙(zhi)-繩(sheng)(sheng)(sheng)（紙(zhi)帶(dai)(dai)(dai)和(he)紙(zhi)繩(sheng)(sheng)(sheng)）絕(jue)(jue)(jue)緣(yuan)、聚(ju)乙烯(xi)(xi)繩(sheng)(sheng)(sheng)-帶(dai)(dai)(dai)絕(jue)(jue)(jue)緣(yuan)、聚(ju)苯(ben)乙烯(xi)(xi)繩(sheng)(sheng)(sheng)－帶(dai)(dai)(dai)絕(jue)(jue)(jue)緣(yuan)和(he)泡沫(mo)聚(ju)乙烯(xi)(xi)絕(jue)(jue)(jue)緣(yuan)等多種。高頻(pin)長(chang)途對稱通信電(dian)(dian)(dian)纜傳輸頻(pin)率高，所以對電(dian)(dian)(dian)纜的(de)結(jie)構性能要求較高。一般采用(yong)(yong)繩(sheng)(sheng)(sheng)－帶(dai)(dai)(dai)絕(jue)(jue)(jue)緣(yuan)的(de)星絞(jiao)四線組(zu)結(jie)構。絕(jue)(jue)(jue)緣(yuan)材料常用(yong)(yong)聚(ju)苯(ben)乙烯(xi)(xi)、聚(ju)乙烯(xi)(xi)。紙(zhi)帶(dai)(dai)(dai)紙(zhi)繩(sheng)(sheng)(sheng)絕(jue)(jue)(jue)緣(yuan)一般用(yong)(yong)于252千赫以下(xia)的(de)低(di)頻(pin)對稱通信電(dian)(dian)(dian)纜。

電(dian)(dian)(dian)(dian)(dian)話(hua)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)是用(yong)于市內、近(jin)(jin)郊和(he)(he)工礦(kuang)企業等較小(xiao)(xiao)范(fan)圍的(de)(de)(de)區域電(dian)(dian)(dian)(dian)(dian)話(hua)連接的(de)(de)(de)對(dui)(dui)(dui)(dui)(dui)稱通(tong)(tong)信電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)，常(chang)稱市內電(dian)(dian)(dian)(dian)(dian)話(hua)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)。其(qi)主要特點(dian)為(wei)(wei)對(dui)(dui)(dui)(dui)(dui)數(shu)多（最(zui)多可達數(shu)千對(dui)(dui)(dui)(dui)(dui)，一(yi)(yi)般(ban)為(wei)(wei)數(shu)百或數(shu)十對(dui)(dui)(dui)(dui)(dui)）。由(you)于使用(yong)頻率低，通(tong)(tong)信距(ju)離近(jin)(jin)，因(yin)此線(xian)(xian)(xian)徑較長(chang)途(tu)通(tong)(tong)信電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)細，一(yi)(yi)般(ban)為(wei)(wei)0.5毫米。電(dian)(dian)(dian)(dian)(dian)話(hua)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)的(de)(de)(de)線(xian)(xian)(xian)組(zu)結構有(you)對(dui)(dui)(dui)(dui)(dui)絞(jiao)(jiao)組(zu)、星絞(jiao)(jiao)組(zu)和(he)(he)復對(dui)(dui)(dui)(dui)(dui)絞(jiao)(jiao)組(zu)3種(zhong)。按其(qi)線(xian)(xian)(xian)心絕(jue)(jue)(jue)緣(yuan)和(he)(he)護(hu)(hu)層材料可分(fen)(fen)為(wei)(wei)紙絕(jue)(jue)(jue)緣(yuan)鉛護(hu)(hu)套電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)、聚乙烯絕(jue)(jue)(jue)緣(yuan)組(zu)合(he)(he)護(hu)(hu)層電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)、油膏充(chong)填防水電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)、全塑(su)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)等。　電(dian)(dian)(dian)(dian)(dian)話(hua)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)中二根絕(jue)(jue)(jue)緣(yuan)導線(xian)(xian)(xian)心按一(yi)(yi)定(ding)節(jie)距(ju)絞(jiao)(jiao)合(he)(he)成(cheng)對(dui)(dui)(dui)(dui)(dui)構成(cheng)一(yi)(yi)個絕(jue)(jue)(jue)緣(yuan)線(xian)(xian)(xian)對(dui)(dui)(dui)(dui)(dui)。線(xian)(xian)(xian)對(dui)(dui)(dui)(dui)(dui)中二根絕(jue)(jue)(jue)緣(yuan)導線(xian)(xian)(xian)心的(de)(de)(de)顏色(se)不同(tong)（一(yi)(yi)般(ban)為(wei)(wei)紅色(se)和(he)(he)白色(se)），以(yi)便接線(xian)(xian)(xian)時(shi)區分(fen)(fen)。電(dian)(dian)(dian)(dian)(dian)話(hua)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)的(de)(de)(de)纜(lan)(lan)(lan)(lan)心結構一(yi)(yi)般(ban)分(fen)(fen)為(wei)(wei)同(tong)心式和(he)(he)單(dan)位式兩種(zhong)（圖3）。同(tong)一(yi)(yi)層中相(xiang)鄰線(xian)(xian)(xian)對(dui)(dui)(dui)(dui)(dui)的(de)(de)(de)絞(jiao)(jiao)合(he)(he)節(jie)距(ju)應不相(xiang)同(tong)，以(yi)減小(xiao)(xiao)通(tong)(tong)話(hua)時(shi)的(de)(de)(de)相(xiang)互影響。在每一(yi)(yi)層中都(dou)設有(you)一(yi)(yi)個標志對(dui)(dui)(dui)(dui)(dui)（分(fen)(fen)別為(wei)(wei)藍色(se)和(he)(he)白色(se)），便于接線(xian)(xian)(xian)時(shi)辨認。在80對(dui)(dui)(dui)(dui)(dui)以(yi)上(shang)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)中往(wang)往(wang)置有(you)預備(bei)線(xian)(xian)(xian)對(dui)(dui)(dui)(dui)(dui)以(yi)替(ti)換不合(he)(he)格線(xian)(xian)(xian)對(dui)(dui)(dui)(dui)(dui)。單(dan)位式電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)以(yi)50對(dui)(dui)(dui)(dui)(dui)或100對(dui)(dui)(dui)(dui)(dui)及相(xiang)應的(de)(de)(de)預備(bei)對(dui)(dui)(dui)(dui)(dui)絞(jiao)(jiao)合(he)(he)成(cheng)一(yi)(yi)個基本單(dan)位，再由(you)若干個基本單(dan)位絞(jiao)(jiao)合(he)(he)成(cheng)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)心。經干燥后(hou)擠(ji)壓上(shang)護(hu)(hu)套制(zhi)成(cheng)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)（見(jian)圖）。

架空敷設的(de)電(dian)(dian)話電(dian)(dian)纜需用自(zi)承(cheng)式，由鋼索承(cheng)受整個(ge)電(dian)(dian)纜的(de)重力。20世紀(ji)60年代以(yi)來，研制出在塑(su)料電(dian)(dian)纜中填充油膏以(yi)防止潮氣和水(shui)分(fen)的(de)防水(shui)型電(dian)(dian)纜。

為了提高通信電(dian)(dian)纜(lan)的防潮(chao)性(xing)(xing)、穩(wen)定性(xing)(xing)，20世紀70年代以來(lai)，在市內電(dian)(dian)話電(dian)(dian)纜(lan)中(zhong)廣泛采用綜(zong)合(he)(he)型電(dian)(dian)纜(lan)護(hu)(hu)層(ceng)(ceng)(ceng)。其基本類型有3種。①Alpeth：纜(lan)心外(wai)擠(ji)(ji)壓(ya)(ya)(ya)一(yi)(yi)層(ceng)(ceng)(ceng)聚(ju)乙烯(xi)(xi)護(hu)(hu)層(ceng)(ceng)(ceng)，再(zai)(zai)搭接地縱向包(bao)裹0.2毫米皺紋鋁帶，充以聚(ju)異丁烯(xi)(xi)絕緣復合(he)(he)物后外(wai)敷一(yi)(yi)層(ceng)(ceng)(ceng)熱(re)塑(su)性(xing)(xing)膠(jiao)粘(zhan)(zhan)層(ceng)(ceng)(ceng)，最外(wai)面擠(ji)(ji)壓(ya)(ya)(ya)一(yi)(yi)層(ceng)(ceng)(ceng)聚(ju)乙烯(xi)(xi)護(hu)(hu)套。②Stalpeth：皺紋鋁帶外(wai)縱包(bao)一(yi)(yi)層(ceng)(ceng)(ceng)皺紋鋼帶，外(wai)覆一(yi)(yi)層(ceng)(ceng)(ceng)熱(re)塑(su)性(xing)(xing)材料，最外(wai)層(ceng)(ceng)(ceng)再(zai)(zai)擠(ji)(ji)壓(ya)(ya)(ya)一(yi)(yi)層(ceng)(ceng)(ceng)聚(ju)乙烯(xi)(xi)護(hu)(hu)套。③Lepeth：纜(lan)心上包(bao)覆一(yi)(yi)層(ceng)(ceng)(ceng)聚(ju)乙烯(xi)(xi)護(hu)(hu)套，其外(wai)敷一(yi)(yi)層(ceng)(ceng)(ceng)粘(zhan)(zhan)性(xing)(xing)熱(re)塑(su)性(xing)(xing)材料，最外(wai)面擠(ji)(ji)壓(ya)(ya)(ya)一(yi)(yi)層(ceng)(ceng)(ceng)鉛管。