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Diagnostic Method for Audio Generation Circuits

IP.com Disclosure Number: IPCOM000109915D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 1 page(s) / 56K

Publishing Venue

IBM

Related People

Drerup, BC: AUTHOR [+2]

Abstract

Disclosed is a circuit that enables diagnostic software running on a computer system to verify the operation of an audio generation circuit. With a minimum of hardware, this circuit verifies the existence of an AC signal at the input of the speaker and the existence of a speaker. (Image Omitted)

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 71% of the total text.

Diagnostic Method for Audio Generation Circuits

      Disclosed is a circuit that enables diagnostic software running
on a computer system to verify the operation of an audio generation
circuit.  With a minimum of hardware, this circuit verifies the
existence of an AC signal at the input of the speaker and the
existence of a speaker.

                            (Image Omitted)

      When the audio generator is on, it drives an AC signal to the
input of the speaker.  This signal is isolated and amplified by
operational-amplifier A1.  The positive portion of the signal is
allowed to pass through rectifier D1.  Capacitor C1 and resistor R2
form a low pass filter which produces a steady state signal from the
pulses that pass through the rectifier.  The values of C1 and R2
should be selected such that the time constant of the filter is
several times larger than the period of the lowest frequency produced
by the audio generator.

      The filtered signal then enters comparator P1 where it is
compared to a threshold voltage.  The comparator output produces a
"high" when the audio signal from the audio generator is large enough
to cause the filtered signal to exceed the threshold.  The comparator
output produces a "low" when the audio signal is small or
non-existent.

      This circuit is also used to detect the existence of the
speaker when the audio signal is off.  The resistance of R1 is chosen
to be much larger than the resi...