▁( as ▁opposed ▁to ▁electric ▁f ences , ▁which ▁carry ▁a ▁current ▁at ▁high ▁voltage ▁that ▁may ▁be ▁le th al ▁in ▁the ▁event ▁of ▁una ut hor ized ▁or ▁defect ive ▁installation ▁or ▁equipment ) ▁but ▁forms ▁a ▁closed ▁loop ▁with ▁a ▁circuit ▁box ▁that ▁transm its ▁a ▁radio ▁signal ▁to ▁the ▁receiver ▁col lar ▁on ▁the ▁dog . ▁As ▁the ▁dog ▁approaches ▁the ▁per imeter ▁the ▁col lar ▁activ ates . ▁ ▁B ark ▁control ▁coll ars ▁B ark ▁control ▁coll ars ▁are ▁used ▁to ▁cur b ▁excess ive ▁or ▁n uis ance ▁b ark ing ▁by ▁deliver ing ▁a ▁shock ▁at ▁the ▁moment ▁the ▁dog ▁begins ▁b ark ing . ▁B ark ▁coll ars ▁can ▁be ▁activ ated ▁by ▁micro phone ▁or ▁v ibration , ▁and ▁some ▁of ▁the ▁most ▁advanced ▁coll ars ▁use ▁both ▁sound ▁and ▁v ibration ▁to ▁eliminate ▁the ▁possibility ▁of ▁extr aneous ▁no ises ▁activ ating ▁a ▁response . ▁ ▁Training ▁coll ars ▁or ▁remote ▁train ers ▁Training ▁coll ars ▁can ▁be ▁activ ated ▁by ▁a ▁hand h eld ▁device . ▁Better ▁quality ▁remote ▁train ers ▁have ▁a ▁large ▁variety ▁of ▁levels ▁and ▁functions , ▁can ▁give ▁varying ▁duration ▁of ▁stim ulation , ▁better ▁quality ▁stim ulation , ▁and ▁have ▁a ▁be ep ▁or ▁v ibration ▁option ▁useful ▁for ▁getting ▁the ▁dog ' s ▁attention . ▁ ▁E - coll ars ▁may ▁be ▁used ▁in ▁conj unction ▁with ▁positive ▁rein for cement ▁and / or ▁util izing ▁other ▁principles ▁of ▁oper ant ▁condition ing , ▁depending