Dub, dawb, ntsuab, liab, xiav, txiv kab ntxwv, xim av, thiab grey - cov xim ntawm rwb thaiv tsev sheaths ntawm cov xov hluav taws xob feem ntau muaj lawv tus kheej lub ntsiab lus. Yog li ntawd, thaum teeb tsa lub teeb pom kev tshiab, ntxiv rau kev tua hluav taws xob hluav taws xob, koj yuav tsum txiav txim siab lub ntsiab lus ntawm txhua qhov xim hlau uas koj ntsib.
Thaum pib, hluav taws xob nyob hauv Tebchaws Meskas tsis muaj cov txheej txheem xim coding, thiab tsis muaj tus qauv rau nws siv kom raug. Tsis ntev tom qab Edison tau qhia txog lub teeb hluav taws xob hauv xyoo 1879, kev lag luam pov hwm tau pib tshaj tawm cov lus qhia txog kev nyab xeeb. Thawj txheej txheem txheej txheem tau tshwm sim hauv xyoo 1881, suav nrog kev hais txog kev muaj peev xwm, rwb thaiv tsev, thiab kev teeb tsa. Txawm li cas los xij, nws tsis tau faib cov xim hlau.
Xyoo 1882, National Fire Underwriters 'Association (NBFU) kuj tau txais kev tswj hwm kev nyab xeeb thaum ntxov. Xyoo 1893, National Electric Insurance Association tau pib sim sib sau ua ke cov txheej txheem kev teeb tsa hluav taws xob sib txawv thiab cov kev cai thoob plaws hauv lub xeev, thov kom muaj lub teb chaws coding tus qauv rau kev tsim cov xaim hluav taws xob thiab cov khoom siv hluav taws xob.
Thawj Txoj Cai Hluav Taws Xob Hauv Tebchaws (NEC) tau thov los ntawm NBFU xyoo 1897, tab sis nws kuj tsis saib xyuas tus qauv ntawm cov teeb meem xim hlau. Tom qab ntawd, xyoo 1928, NEC tau hloov kho nws cov qauv, ib qho yuav tsum tau ua yog tsim cov xim xim rau cov xov hlau hauv av, uas tau los ua xim dawb lossis ntuj grey. Cov xim no kuj raug txwv tsis pub siv rau ntawm cov xov hlau nyob thiab nruab nrab.
Ib qho ntxiv xim coding system tau qhia los ntawm NEC hauv xyoo 1937, tso cai rau xim - cov xov hlau uas siv tau rau hauv "ntau- cov kab hluav taws xob," qhia tias peb - cov kab hluav taws xob yuav tsum siv cov xov hlau dub, liab, thiab dawb. Ntau ceg ntoo tuaj yeem muaj xim ntxiv, xws li daj thiab xiav.
Xyoo 1953, NEC tau hloov cov xim av rau xim ntsuab lossis liab qab. Ntsuab kuj raug txwv tsis pub siv rau hauv cov xov hlau hluav taws xob (xws li cov xov hlau nyob thiab nruab nrab).
NEC's 1971 version tau siv cov xim ntau-txoj kev coding, txawm tias dawb, ntuj grey, ntsuab, thiab daj- ntsuab kab txaij tseem khaws cia, thiab cov xim no kuj raug txwv tsis pub siv hauv av. Cov txheej txheem no tau tso tseg cov xim nruj xim coding uas yuav tsum tau muaj rau cov xov hlau hluav taws xob vim tias tsis muaj xim txaus kom paub qhov txawv ntawm cov tshuab, qhov hluav taws xob, thiab cov khoom siv hluav taws xob.
Tam sim no hauv Tebchaws Meskas, cov xov hlau hauv av yog ntsuab, daj - ntsuab striped, los yog liab qab hlau; nruab nrab ntawm cov xov hlau yuav tsum yog dawb lossis grey; thiab nyob ntawm tej zaum yuav dub, liab, xiav, daj, txiv kab ntxwv, los yog daj, nyob ntawm qhov voltage.
Cov qauv xim no yog US-raws li; Lwm lub tebchaws muaj cov lej sib txawv (Canada's zoo sib xws). Piv txwv li, Australia thiab New Zealand siv tib cov av xaim xim ib yam li Asmeskas, thiab lawv cov xov hlau nruab nrab yog xiav lossis dub. Tsis tas li ntawd, cov xov hlau nyob tau tuaj yeem yog xim lwm yam tsis yog hauv av thiab nruab nrab. Liab thiab xim av yog pom zoo xim rau ib zaug - cov xov hlau theem, thaum liab, dawb, thiab xiav yog pom zoo xim rau ntau-theem nyob hlau.
Lub UK tsis ntev los no (2004) tau hloov nws txoj kev ua raws li International Electrotechnical Commission (EC). Lawv cov xim av hauv av (daj- kab txaij ntsuab) tseem tsis hloov, tab sis cov xim nruab nrab ntawm cov xaim hloov ntawm dub mus rau xiav. Ib yam li ntawd, ib zaug - cov xov hlau txuas, yav dhau los liab, tam sim no xim av. Tsis tas li ntawd, cov cim thiab xim rau ntau- cov kab hauv UK tau hloov pauv: L1 hloov ntawm liab mus rau xim av, L2 los ntawm daj mus rau dub, thiab L3 los ntawm xiav rau grey.
