Apple Macintosh PowerBook 1400 - Manual (Page 61)

Connecting sound input and output devices
Your computer has a built-in microphone. For information on using the
microphone to record sounds, see the “Sound” topic 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. This port accepts a standard stereo miniplug like that used to
attach headphones to a portable tape player. You cannot use the internal
microphone and an external sound input device at the same time. For
instructions on selecting a sound device in the Monitors & Sound control
panel, see the “Sound” topic of Mac OS Guide, available in the
Guide (h) menu.
The Macintosh PowerBook also has a stereo sound output port (marked with
the - icon) to which you can connect externally powered speakers, an
amplifier, headphones, or other audio output devices. The sound output port
accepts a standard stereo miniplug, like that used to attach headphones to a
portable tape player.
Microphone
61 Connecting Additional Equipment and Changing BookCovers