The test beeper generates a sinusoidal signal with a frequency of 1,000 Hz, a common test frequency for audio amplifiers. It consists of a classical Wien- Bridge oscillator (also known as a Wien-Robinson oscillator). The network that determines the frequency consists here of a series connection of a resistor and capacitor (R1/C1) and a parallel connection (R2/C2), where the values of the resistors and capacitors are equal to each other. This network behaves, at the oscillator frequency (1 kHz in this case), as two pure resistors. The opamp (IC1) ensures that the attenuation of the net- work (3 times) is compensated for. In principle a gain of 3 times should have been sufficient to sustain the oscillation, but that is in theory. Because of tolerances in the values, the amplification needs to be (automatically) adjusted. Circuit diagram: Test Beeper For Your Stereo circuit Diagram Instead of an intelligent amplitude controller we chose for...