Two square waves with different phases and high and low levels can be obtained at J2 output. The second TL084 can be in the switching state, the voltage regulator plays the role of limiting the voltage amplitude, and the varactor plays the role of filtering out higher harmonics.

The so-called switching state, that is, the amplifier circuit works between the saturation region and the load stop region, and the output switches between the high level and the low level, that is, the square wave.