ios ▁at ▁the ▁same ▁location , ▁some ▁protocol ▁has ▁to ▁be ▁established ▁so ▁that ▁one ▁port able ▁transm itting ▁doesn ' t ▁activ ate ▁two ▁or ▁more ▁mobile ▁radio ▁transmit ters . ▁Motor ola ▁uses ▁a ▁hierarchy ▁system ▁with ▁P AC * RT , ▁each ▁repe ater ▁transm its ▁a ▁tone ▁when ▁it ▁is ▁turned ▁on , ▁so ▁the ▁last ▁one ▁on ▁site ▁that ▁turns ▁on ▁is ▁the ▁one ▁that ▁gets ▁used . ▁This ▁is ▁so ▁several ▁of ▁them ▁are ▁not ▁on ▁at ▁once . ▁ ▁Ve h icular ▁repe aters ▁are ▁complex ▁but ▁can ▁be ▁less ▁expensive ▁than ▁design ing ▁a ▁system ▁that ▁covers ▁a ▁large ▁area ▁and ▁works ▁with ▁the ▁weak ▁signal ▁levels ▁of ▁hand - h eld ▁rad ios . ▁Some ▁models ▁of ▁radio ▁signals ▁suggest ▁that ▁the ▁transmit ters ▁of ▁hand - h eld ▁rad ios ▁create ▁received ▁signals ▁at ▁the ▁base ▁station ▁one ▁to ▁two ▁orders ▁of ▁magnitude ▁( 1 0 ▁to ▁ 2 0 ▁de ci b els ▁or ▁ 1 0 ▁to ▁ 1 0 0 ▁times ) ▁we aker ▁than ▁a ▁mobile ▁radio ▁with ▁a ▁similar ▁transmit ter ▁output ▁power . ▁ ▁S iting ▁as ▁part ▁of ▁system ▁design ▁ ▁Radio ▁repe aters ▁are ▁typically ▁placed ▁in ▁locations ▁which ▁maxim ize ▁their ▁effect iveness ▁for ▁their ▁intended ▁purpose : ▁ ▁" L ow - level " ▁repe aters ▁are ▁used ▁for ▁local ▁communic ations , ▁and ▁are ▁placed ▁at ▁low ▁alt itude ▁to ▁reduce ▁inter ference ▁with ▁other ▁users ▁of ▁the ▁same ▁radio ▁frequencies .