IBM 4840-563 System Reference Manual page 23

The audio subsystems provides the following functions:
Audio Codec 97 Revision 2.3 compliant Audio
Full duplex capability
The audio subsystem consists of the following elements:
Realtek Codec AL202A integrated headphone amplifier
Headphone and microphone jack
External amplified speaker assembly
Implementation Notes:
Volume control is through normal Windows multimedia controls in combination with a volume
control on the speaker unit.
Bass/Treble slides in windows volume control will not be functional
This subsystem can be disabled in through Setup.
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