Non-Return-to-Zero Inverted A method for transmitting and recording data so that it keeps the sending and receiving clocks synchronized. This is especially helpful in situations where bit stuffing is employed — the practice of adding bits to a data stream so it conforms with communications protocols. These added bits can create a long string of similar bits, which register to the receiver as a single, unchanging voltage. Since clocks adjust on voltage changes, they’ll lag behind true time. NRZI ensures that after a 0 bit appears, the voltage will immediately switch to a 1 bit voltage level. These voltage changes allow the sending and receiving clocks to synchronize.