The trapezoid wave ramps linearly to a positive reference point, holds at the reference point, ramps linearly to a negative reference point, holds at the negative reference point, and repeats. A trapezoid wave is like a cross between a triangle wave and a square wave; effectively a slewing square wave. The waveform is symmetrical, meaning that the time spent slewing positive, holding positive, slewing negative, and holding negative are all equal, and that the slope of the positive ramp is equal and opposite the slope of the negative ramp.