To speed testing, the circuit generates a composite audio signal comprising 10 sine waves of 10 different equal-amplitude frequencies across the audio band. Values stored in EPROM determine the frequencies.
Testing the frequency response of an audio device typically requires a sine-wave oscillator, an ac voltmeter or an oscilloscope, and an operator to record the response of the device at several frequencies across the audio band. Complicating this test is the inability of many audio oscillators to maintain a constant output level as the frequency varies, particularly when switching between frequency ranges.
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