Wanpela jenerel-pepos rilei em i wanpela bikpela samting bilong bosim lektrik we ol i save yusim planti taim long wok bilong bosim pawa. Em i save bosim opim na pasim bilong ol 'circuit' o 'switch' bihainim ol senis long ol 'input electrical signals' (olsem 'voltage' na 'current') o ol 'non-'elektrikel signals (olsem tempereja na presa), na i save mekim wok bilong bosim na lukautim em yet.
Long lukluk bilong wok prinsipol, ol jeneral-pepos rilei i save wok pastaim long prinsipol bilong elektromagnetik induksen. Taim koil i kisim pawa, wanpela 'electromagnetic fos' i pulim 'armature', na dispela i mekim ol 'contact' i pas o op. Long ol komon elektromagnetik jeneral-pepos rilei, taim bilong pulim-in i save stap namel long tenpela i go inap handet milisekon, na taim bilong rilis i klostu wankain, tasol ol spesifik veliu i ken senis bihainim ol spesifikesen na model bilong rilei.
Ol jenerel-pepos rilei i gat kain kain kontek, olsem ol kontek we i save op, ol kontek we i save pas, na ol kontek we i save senis. Ol 'open contacts' i save op taim 'relay' i no wok na ol i save pas bihain long ol i kirapim; ol 'contact' we i save pas i save pas taim 'relay' i no wok na op bihain long wok; ol 'changeover contacts' i save bungim wok bilong tupela, na dispela i mekim na 'circuit switching' i ken kamap. Long ol wok we ol i ken mekim, ol i ken makim stretpela kain kontek bihainim ol samting ol i nidim long bosim. Koil resistens bilong wanpela jenerel-pepos rilei em i wanpela bikpela samting, we i save mekim pawa konsumsen na sensitiviti bilong en i senis. Koil resistens bilong wanpela liklik jenerel-pepos rilei i save stat long sampela handet ohm i go inap long sampela tausen ohm, tasol koil resistens bilong wanpela haia-pawa rilei i liklik tru. Dispela em bilong mekim inap pawa i ken go insait long kamapim 'electromagnetic force' we ol i nidim. Pasin bilong senisim envairomen bilong wanpela jenerel-pepos rilei em i bikpela samting tu; em i mas inap long wok gut aninit long sampela envairomen kondisen, olsem tempereja, humiditi, na altitude.
Olsem, sampela 'general-purpose relays inap long wok gut insait long wanpela tempereja we i stap namel long -25 digri i go inap 70 digri, wantaim 'relative humidity' inap long 95%, na inap long senis long ol ples antap inap 2000 mita o moa yet. Ol i ken brukim ol 'general-purpose relays' long ol 'control relays' na 'protection relays'. Ol i save yusim ol 'control relays' long ol 'automatic control system' bilong bosim ol 'circuits'; ol i save yusim ol 'protection relays' long lukautim ol lektrikel ikwipmen long 'overcurrent', 'overvoltage', na 'undervoltage', na ol i save katim 'circuit' hariap taim ol samting i no stret i kamap.
