▁skin . ▁( The ▁col lar ▁must ▁be ▁fitted ▁according ▁to ▁the ▁manufact urer ' s ▁instructions .) ▁Local ▁hum id ity ▁and ▁individual ▁variation ▁in ▁coat ▁density , ▁skin ▁thick ness ▁and ▁surface ▁conduct ivity , ▁also ▁affect ▁the ▁delivery ▁of ▁the ▁stim ulation . ▁ ▁The ▁wave form , ▁its ▁frequency , ▁the ▁pul se ▁rate , ▁current , ▁voltage ▁and ▁imped ance ▁are ▁important ▁determin ants ▁of ▁likely ▁response . ▁" Many ▁e − coll ars ▁appear ▁to ▁shift ▁intensity ▁levels ▁by ▁alter ing ▁the ▁pul se ▁duration ▁or ▁repet ition ▁rate ▁while ▁keeping ▁the ▁output ▁current ▁and ▁voltage ▁relatively ▁constant , ▁depending ▁on ▁the ▁electro de − sk in ▁load ." ▁( L inds ay ▁ 2 0 0 5 , ▁p .   5 7 3 ). ▁ ▁Ind ividual ▁variations ▁in ▁temper ament , ▁pain ▁sens itivity ▁and ▁sus cept ibility ▁to ▁start le ▁of ▁dogs , ▁means ▁that ▁settings ▁must ▁be ▁carefully ▁adjust ed ▁to ▁produce ▁a ▁stim ulation ▁that ▁is ▁perce ived ▁by ▁the ▁dog ▁as ▁only ▁just ▁a vers ive ▁enough ▁to ▁stop ▁the ▁dog ▁eng aging ▁in ▁the ▁unw anted ▁behavior . ▁Norm ally ▁sal ient ▁stim uli , ▁such ▁as ▁no ises , ▁commands ▁and ▁even ▁shock s , ▁may ▁have ▁no ▁effect ▁on ▁a ▁dog ▁that ▁is ▁highly ▁ar oused ▁and ▁focused ▁on ▁an ▁activity ▁such ▁as ▁hunting . ▁ ▁Pot ential ▁to ▁cause ▁harm ▁In ▁ 1 9 8 0 ▁( re vised ▁ 1 9 8 7 ), ▁the