Is-sistema tal-wajers protetti oriġinaw mill-Ewropa. Huwa saff ta 'lqugħ tal-metall miżjud ma' barra tas-sistema ordinarja tal-wajers mhux protetti. Ir-riflessjoni, l-assorbiment u l-effett tal-ġilda tas-saff tal-ilqugħ tal-metall jintużaw biex jipprevjenu interferenza elettromanjetika u radjazzjoni elettromanjetika. Is-sistema ta 'lqugħ tuża b'mod komprensiv Il-prinċipju tal-bilanċ ta' par mibrum u l-effett ta 'lqugħ tas-saff ta' lqugħ, għalhekk għandha karatteristiċi ta 'kompatibilità elettromanjetika (EMC) tajba ħafna.
Kompatibilità elettromanjetika (EMC) tfisser li tagħmir elettroniku jew sistemi tan-netwerk għandhom ċerta kapaċità li jirreżistu l-interferenza elettromanjetika, u fl-istess ħin ma jistgħux jiġġeneraw radjazzjoni elettromanjetika eċċessiva. Jiġifieri, huwa meħtieġ li l-apparat jew is-sistema tan-netwerk jistgħu jaħdmu b'mod normali f'ambjent elettromanjetiku relattivament ħarxa, u fl-istess ħin ma jistgħux jirradja mewġ elettromanjetiku eċċessiv biex jinterferixxi mat-tħaddim normali ta 'apparati u netwerks oħra tal-madwar.
The balanced characteristics of U/UTP (unshielded) cables are not only determined by the quality of the components themselves (eg twisted pairs), but are also affected by the surrounding environment. Because metal around U/UTP (unshielded), hidden "ground", pulling during construction, bending, etc. will destroy its balance characteristics, thereby reducing EMC performance.
Għalhekk, hemm soluzzjoni waħda biss biex tikseb karatteristiċi bilanċjati dejjiema: art il-qlub kollha b'saff żejjed ta 'fojl tal-aluminju. Il-fojl tal-aluminju jżid il-protezzjoni mal-qlub fraġli tal-pari mibrumin-, filwaqt li joħloq artifiċjalment ambjent ibbilanċjat għall-kejbils U/UTP (mhux protetti). B'hekk jiffurmaw dak li issa nsejħu kejbil protett.
Il-prinċipju tal-ilqugħ tal-kejbil protett huwa differenti mill-prinċipju tal-kanċellazzjoni bilanċjata tal-par mibrum. Il-kejbil protett huwa li żżid saff wieħed jew tnejn ta 'fojl tal-aluminju fuq barra tal-erba' pari ta 'pari mibrumin, u juża l-metall biex jirrifletti, jassorbi u l-prinċipji tal-effett tal-ġilda tal-mewġ elettromanjetiku (l-hekk imsejjaħ-tendenza) . L-effett tal-ġilda jfisser li d-distribuzzjoni tal-kurrent fis-sezzjoni trasversali tal-konduttur għandha t-tendenza li titqassam fuq il-wiċċ tal-konduttur biż-żieda tal-frekwenza. L-interferenza elettromanjetika tidħol fil-kejbil, iżda tipprevjeni wkoll li s-sinjal intern jirradja 'l barra, u tinterferixxi max-xogħol ta' tagħmir ieħor.
Experiments show that electromagnetic waves with frequencies exceeding 5MHz can only pass through 38μm thick aluminum foil. If the thickness of the shielding layer exceeds 38 μm, the frequency of electromagnetic interference that can enter the cable through the shielding layer is mainly below 5MHz. For low-frequency interference below 5MHz, the balance principle of twisted pair can be applied to effectively cancel.
According to the earliest definition of wiring, it is divided into two types: unshielded cable-UTP and shielded cable-STP. Later, with the development of technology and different craftsmanship, many different types of shielding were derived. F/UTP Foil Screened Cable Single-layer aluminum foil shielding structure 2． Foil and Braid Screened Cable Double-layer shielding structure of aluminum foil and copper braid a) SF/UTP aluminum foil and copper braid wrapped on the outer layer of four pairs of wires at the same time b) S/FTP (PIMF) wire pair single pair of aluminum foil shielding plus The copper braided mesh PIMF =Pair in Metal Foil wrapped on the outer layer of the four pairs of wires.
The shielded cable's resistance to external interference is mainly reflected in: the integrity of signal transmission can be guaranteed by the shielding system. The shielded wiring system can prevent the transmitted data from being affected by external electromagnetic interference and radio frequency interference. Electromagnetic Interference (EMI) is mainly low frequency interference. Motors, fluorescent lamps and power lines are common sources of EMI. Radio frequency interference (RFI) is high frequency interference, mainly radio frequency interference, including radio, television broadcast, radar and other wireless communications.
Għar-reżistenza għall-interferenza elettromanjetika, l-ilqugħ immaljat huwa l-aktar għażla effettiva, jiġifieri, l-ilqugħ tal-malji tal-metall, minħabba r-reżistenza kritika baxxa tiegħu. Għall-interferenza tal-frekwenza tar-radju, l-ilqugħ tal-fojl tal-metall huwa l-aktar effettiv, minħabba li d-distakk maħluq mill-ilqugħ tal-malji tal-metall jippermetti li s-sinjali ta 'frekwenza għolja - jidħlu u joħorġu liberament. Għall-qasam ta 'interferenza mħallta ta' frekwenza għolja u baxxa, għandu jintuża l-metodu ta 'lqugħ magħqud ta' saff ta 'fojl tal-metall u malji tal-metall, jiġifieri, il-kejbil protett ta' saff doppju-fil-forma ta 'S/FTP, li jista' jagħmel l-ilqugħ tal-malji tal-metall adattat għall-interferenza fil-medda ta 'frekwenza baxxa, u l-ilqugħ tal-fojl tal-metall Adattat għal interferenza fil-medda ta' frekwenza għolja.
The single-layer thickness of the aluminum foil shielding layer in the IBM ACS shielded cable reaches 50-62 μm, which has a more complete shielding effect. At the same time, because only a single layer of shielding is used, it will be simpler for construction, easy to install, and not easy to cause artificial damage during the construction process, and the thickness of the aluminum silk can withstand greater destructive force. This can provide users with higher quality transmission performance.
