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Path: utzoo!linus!decvax!harpo!ihnp4!drutx!drufl!pmr
From: pmr@drufl.UUCP (Rastocny)
Newsgroups: net.audio
Subject: Re: Well!  Finally, a 20th Century disk playing device!
Message-ID: <755@drufl.UUCP>
Date: Wed, 28-Dec-83 09:58:49 EST
Article-I.D.: drufl.755
Posted: Wed Dec 28 09:58:49 1983
Date-Received: Sun, 8-Jan-84 00:46:05 EST
References: <725@decvax.UUCP>
Organization: AT&T Information Systems, Denver
Lines: 14

Who was the manufacturer?  I'd be very interrested in hearing this
gizmo.  Please post information you get to the net.

About your digital comments, remember that CD players AND this gadget
probably both use similar digital techniques.  From your description, a
zero-crossing detector is most likely used to scan the groove undulations
in playback.  This circuit produces a square wave analog of the record
"bumps."  Each time the laser's companion photodetector "sees" a
reflection it produces an output level change.  (A digital signal from
an analog source.)  About the same low-pass filtering problems would apply
to this gadget as they do to CD players.

Phil Rastocny
..!drufl!pmr