This circuit can output sine, square, and triangular signals of from 15 Hz to 25kHz in three ranges. The circuit is built around an 8038 function generator that produces the triangular- and square-wave out-puts directly from an oscillator. The triangular output is then processed to develop the sine waze. While that method doesn't provide a sufficiently low level of distortion to let you make distortion measurements on audio gear, the degree of purity is high enough for frequency-response tests and a lot of other audio analysis. Three switched capacitors, C2 to C4, set the circuits frequency range via switch S1. Variable resistor R9 and resistor R1 provide the voltage for controlling the charge and discharge rates of the timing capacitor selected. Resistors R4 to R6 control the charge and discharge currents. Resistor R5 can be adjusted to provide a 1.1 mark/space ratio