Ngekhulu le-18, ososayensi babheka ugesi kanye ne-magnetism njengezinto ezimbili ezingahlobene ngokuphelele. Ngemva kokuba isazi sefiziksi saseDenmark uJohann Gerhard Oersted sithole umphumela kazibuthe wamandla kagesi ngo-1820, isazi sefiziksi saseBrithani uMichael Faraday sathola ukufakwa kwe-electromagnetic induction ngo-1831. Lokhu okutholakele kwaqinisekisa ukuthi amandla kagesi namandla kazibuthe kungashintshwa, kwabeka isisekelo sokuthuthukiswa kwakamuva kwamamotho kagesi namajeneretha; Ngakho isintu sangena enkathini kagesi ngenxa yalezi ziqalo. Ngawo-1830, isazi sefiziksi saseMelika uJoseph Henry sasungula i-relay ngenkathi sicwaninga ukulawulwa kwesifunda sisebenzisa isenzakalo sokungeniswa kwe-electromagnetic. Ama-relay akuqala kakhulu ama-electromagnetic relays, asebenzisa isenzeko sokukhiqiza nokunyamalala kwamandla kazibuthe kumazibuthe kagesi lapho enikwa amandla futhi{7}}enikwa amandla okulawula ukuvuleka nokuvalwa kwesinye{8}}i-voltage ephezulu, ephezulu{9}}yamanje. Ukufika kwayo kwenze ukusebenza kahle kokulawulwa kude nokuvikela amasekethe. I-relay iyinto esungulwe kakhulu emlandweni wesayensi yesintu nobuchwepheshe; akusona isisekelo sobunjiniyela bakagesi kuphela kodwa futhi isisekelo esibalulekile sobuchwepheshe be-elekthronikhi kanye nobuchwepheshe be-microelectronics.
I-relay iyidivayisi yokulawula kagesi okuthi, lapho inikezwa inani elicacisiwe lokokufaka futhi ibanjwe isikhathi esanele, ibangele ushintsho olunqunywe kusengaphambili lwenani elilawulwayo kumjikelezo ophumayo kagesi. Uma inani lokokufaka lehla liye ezingeni elithile futhi libanjwe isikhathi eside ngokwanele, libuyela esimweni salo sokuqala. Umgomo wayo oyinhloko ungalandelelwa emuva ekuthuthukisweni kozibuthe kagesi ekhulwini le-19.
