This circuit produces a sinusoidal signal whose frequency can be calculated using the formula in the diagram. Next to this formula we have the calculated values for a frequency of 1 kHz. The power supply does not need to be symmetrical, but its voltage influences the distortion of the generated waveform, giving preference to values between 12 and 15 V. The adjustment of the symmetry of the waveform and its fidelity is done in the trimpot. The reference voltage can be obtained through a divider with two 10k ohm resistors in series.