Nyob rau hauv lub xyoo pua 18th, cov kws tshawb fawb tau txiav txim siab tias hluav taws xob thiab hlau nplaum yog ob lub cev tsis sib xws. Tom qab Danish physicist Johann Gerhard Oersted nrhiav tau cov magnetic nyhuv ntawm hluav taws xob tam sim no nyob rau hauv 1820, British physicist Michael Faraday nrhiav electromagnetic induction nyob rau hauv 1831. Cov kev tshawb pom no tau lees paub tias hluav taws xob hluav taws xob thiab hluav taws xob sib nqus tuaj yeem hloov pauv, nteg lub hauv paus rau kev txhim kho tom qab ntawm hluav taws xob motors thiab generators; tib neeg yog li nkag mus rau lub hnub nyoog hluav taws xob ua tsaug rau cov kev tsim kho no. Nyob rau xyoo 1830, tus kws tshawb fawb Asmeskas tus kws tshawb fawb Joseph Henry tau tsim lub relay thaum kawm kev tswj xyuas hluav taws xob siv qhov tshwm sim ntawm electromagnetic induction. Cov relays ntxov tshaj plaws yog electromagnetic relays, uas siv cov phenomenon ntawm tiam thiab ploj ntawm magnetic quab yuam nyob rau hauv electromagnets thaum energized thiab de-energized los tswj qhov qhib thiab kaw ntawm lwm high -voltage, high- tam sim no Circuit Court. Nws qhov kev tshwm sim tau ua rau kev ua haujlwm du ntawm cov chaw taws teeb tswj thiab kev tiv thaiv circuits. Lub relay yog ib tug zoo invention nyob rau hauv keeb kwm ntawm tib neeg science thiab technology; nws tsis yog tsuas yog lub hauv paus ntawm hluav taws xob engineering tab sis kuj yog lub hauv paus tseem ceeb rau kev siv tshuab hluav taws xob thiab microelectronics technology.
Lub relay yog ib qho khoom siv hluav taws xob tswj hluav taws xob uas, thaum muab cov khoom tso tawm kom muaj nuj nqis thiab tuav lub sijhawm txaus, ua rau muaj kev hloov pauv hloov pauv hauv cov tswj kom muaj nuj nqis hauv hluav taws xob tawm hluav taws xob. Thaum cov tswv yim kom muaj nuj nqis nqis mus rau ib theem thiab tau tuav lub sijhawm ntev txaus, nws rov qab mus rau nws lub xeev thawj zaug. Nws lub hauv paus ntsiab lus tseem ceeb tuaj yeem taug qab mus rau qhov kev tawg ntawm electromagnetism hauv xyoo pua 19th.
