Hauv Teb Chaws Asmeskas ob peb hnub dhau los, cov xaim hauv av yog ntsuab, daj-ntsuab kab txaij lossis liab qab hlau, cov hlau nruab nrab yuav tsum yog xim dawb lossis grey, thiab cov xaim hluav taws xob yuav yog xim dub, liab, xiav, daj, txiv kab ntxwv lossis daj. Cov xim tshwj xeeb nyob ntawm qhov voltage.
Cov qauv xim no yog rau Tebchaws Meskas, thiab lwm lub tebchaws cov lej sib txawv (Canada zoo ib yam li Tebchaws Meskas). Piv txwv li, Australia, New Zealand thiab Tebchaws Meskas muaj tib lub hauv av hlau xim, thiab lawv cov hlau nruab nrab yog xiav lossis dub. Ntxiv mus, cov hlau nyob yuav ua tau tej yam xim uas tsis yog hauv av hlau thiab cov hlau nruab nrab. Liab thiab xim av yog pom zoo xim rau ib-theem xaim, thiab liab, dawb, thiab xiav yog pom zoo xim rau ntau theem tam sim no them xov hlau.
Lub UK tau tsis ntev los no (2004) hloov nws txoj kev ua raws li International Electrotechnical Commission (EC). Lawv cov xim av xaim (xim daj-ntsuab kab txaij) tseem tsis hloov pauv, thiab cov xim nruab nrab ntawm cov xaim xim hloov ntawm dub mus rau xiav. Ib yam li ntawd, ib-theem xaim siv liab tab sis tig xim av. Tsis tas li ntawd, cov cim thiab xim ntawm cov kab polyphase hauv UK kuj tau hloov: L1 hloov ntawm liab mus rau xim av, L2 hloov ntawm daj mus rau dub, thiab L3 hloov ntawm xiav mus rau grey.
