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Built-in Microphone
The built-in microphone is located at the bottom of the left speaker grill.
The sound signal from the built-in microphone goes through a dedicated preamplifier that raises its nominal
30 mV level to a nominal 150 mV (peak-to-peak) signal to the sound circuitry. That signal level assures good
quality digitizing without driving the analog input into clipping.
Audio Input Jack
The audio input jack is a 3.5 mm mini phone jack that accepts line-level stereo signals. It also accepts a stereo
miniplug-to-RCA cable adapter for connecting stereo equipment to the computer.
The sound input jack signal connections are
● tip: audio left channel
● ring: audio right channel
● sleeve: audio ground
Modem Activity Sound Signals
Modem activity sound signals from the communications slot are sent to the Snapper sound circuitry as 8-bit
digital data.
Sound Outputs
The sound system sends sound output signals to the built-in speakers and the external sound output jack.
Headphone Jack
The headphone jackis locatedon the left sideof the computer. The headphone jackprovides enough current
to drive a pair of low-impedance headphones. It can also be used as a line-level output.
The headphone jack has the following electrical characteristics:
● impedance suitable for driving standard 32-ohm headphones
● output level 2.0 V peak-to-peak (1.41 V RMS)
● signal-to-noise (SNR) 90 dB unweighted (typical)
● total harmonic distortion (THD) 0.03% or less
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Sound System
Legacy Document | 2003-03-01 | © 2003 Apple Computer, Inc. All Rights Reserved.
CHAPTER 3
Devices and Ports