Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!blob
From: blob@Apple.COM (Brian Bechtel)
Newsgroups: comp.sys.mac.hardware
Subject: Sound input on the new machines
Keywords: IIsi, LC, microphones, audio
Message-ID: <45666@apple.Apple.COM>
Date: 15 Oct 90 22:25:07 GMT
Organization: Apple Computer Inc., Cupertino, CA
Lines: 32

I saw this on Applelink and thought some people might be interested.  I
know nothing more than what's listed.

--Brian Bechtel		blob@apple.com		"My opinion, not Apple's"

Macintosh LC and Macintosh IIsi sound input
 
Macintosh LC and Macintosh IIsi have built-in mono 8-bit sound input
circuitry. This hardware is supported by the System 7.0 Sound Manager
which is included in System 6.0.7.

An electret microphone, plastic holders to attach the microphone to the
front of a monitor or clip-on to clothing, and an attenuated RCA
adaptor cable will be included with the CPU.  The microphone has a male
miniature stereo phone connector.  Customers can use any commercially
available microphone which does not require an external power source.

The RCA adapter cable, with a male miniature stereo phone connector on
one end and two female RCA connectors on the other, has a special
attenuator on it that steps down the voltage level of the incoming
signal.  Devices such as CD players or tape players provide line out
signals at a higher level than the 20 millivolt - 600= impedence
expected by the sound input circuitry.  If you use a non-attenuated RCA
adaptor cable in the audio in jack, you will not hurt the CPU and it
will still digitize the signal, but it will be very distorted (sort of
like a Jimi Hendrix guitar riff).

If you use the attenuated RCA adapter cable as a audio out cable, it
may or may not work, depending on what youUre connecting to.   Using a
standard RCA adapter cable is recommended for audio out.  If the
microphone is plugged into the audio out jack no sound will come out of
the jack or the internal speaker.