Apple PowerBook (3400 series) - Manual (Page 72)

Connecting sound input and output devices
Your computer has a built-in microphone. In addition, you can connect a
PlainTalk microphone to the external sound input port. (You can also connect
a standard line-level input microphone, although it is not suitable for speech
recognition.)
For information on using the microphone to record sounds, see the “Sound”
topic area of Mac OS Guide, available in the Guide (h) menu.
Your Macintosh PowerBook also has a stereo sound input port (marked with
the √ icon) for connecting external sound input devices that provide line-
level output. You cannot use the internal microphone and an external sound
input device, such as a PlainTalk microphone, at the same time. For
instructions on selecting a sound device, see the “Sound” topic area of Mac
OS Guide, available in the Guide (h) menu.
Microphone
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