converts square wave to a sine wave. The square signal is passed into the cascading RC network, where the time consant (Tau) is 20K*2uF equalling 40 (ms). Because the period of the square wave is 250ms and half of the period is 125ms, that means the capacitors can charge up to about approx 95% of the input voltage due to half of the square wave period being more than 3 times the RC time constant (ie. 0.5*T = 125 ms > 3*R*C =120 ms). After the small sinusoidal is produced, it is then fed into a voltage follower (buffer) and then into a negative feedback Op-Amp configuration with a variable mulltiplier (potentiometer).
