The emergency Jack Protocol (EJP) was a type of override device invented by Danielle Wright, some time after the establishment of the Truce between Zion and the machines. It forcibly exits a person out of the Matrix instantly without the use of a hardline and the person avoids dying. However, when the Machines made war with Zion again, they used a database containg some of the known Zionite RSI signatues, they were able to speifically lock on and kill any person with his/her correpsonding signature, and bypassing the safty measure. (Zion: Life and Death (Episode 8.3)