Potentiometer at the center of the diagram affects to the frequency of the output signal Potentiometer at the left top corner changes the slope of waveform linear pieces from saw with the steep rising edge through symmetrical triangular signal to saw with steep falling edge. The voltage of time dependance for the initially discharged capacitor charging through connected in series resistor is of the form: U(t) = U_0(1 - exp(-t/RC)). The natural way to obtain (almost)linear dependance voltage of time is to take small enough interval of time for specified function U(t) where the difference between U(t) and its tangent at zero is insignificant and since under this assumptions the range of voltage variation is also small then scale/amplify it up to the necessary value. This circuit intentionally designed for single-polarity power supply however the similar circuit with dual polarity supply for OA's technically a little bit easier to design. Actually in this circuit the middle point of supply voltage is created using a pair of 10K resistors. You may assemble this circuit taking operational amplifiers with any real possible characteristics say with open-loop gain in order only of several hundred and it will be work quite well.
