This "relatively simple circuit" generates a sinusoidal signal with the help of two counters, two D-flip-flops, one DAC and several logic gates. The left counter (slave) works under the control of the right counter (master). The master stops the account of the slave so as to cut off the top and bottom of the saw. During pauses, the master shortens the period of the clock generator in half to shorten the flat parts of the signal at the DAC output. The low-pass filter turns the truncated saw into a sinusoidal signal. The ideal ellipse in the X-Y diagram proves the sinusoidal nature of the output signal. The period of the ideal sine oscillator is equal to the period of the signal at the output of the DAC (translated by Google).
