This is a graph showing 0s and 1s using high and low voltages. The top square wave rises to a height of 1 for one unit of time, from a base of 0. It then drops to 0 for one unit of time, rises to 1 for one unit of time, drops to 0 for two units of time, rises to 1 for one unit of time, finally dropping to 0. Two dotted horizontal lines run at 1/3 and 2/3 of the height of the wave. The distance between the top line and the maximum height of the square waves is labelled “high voltages, 1”. The distance between the bottom line and the base line is labelled “low voltages, 0”. The distance between the two lines is labelled “gap”.