Some signaling techniques are easier for the receiving circuitry to sense than others. One technique is called NRZL (Non-Return to Zero, Level) which encodes 1s and 0s in a fashion that seems very obvious. Fig. 23.2.1 shows a data byte transmitted in this fashion. 0 is encoded as a certain voltage level, say +5 Volts, while 1 is encoded as a higher voltage level, such as +12 V. 01001110 is encoded as a sequence of these voltage levels. The sharp transitions from 5 to 12 and back down are actually simplifications because voltage cannot rise infinitely swiftly, but for our purposes the rise is fast enough relative to the "bit width" that it appears to be a sharp square wave.