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From: taras@utgpu.UUCP
Newsgroups: sci.electronics
Subject: Re: 3800 Hz notch filter [will] be used on CD masters
Message-ID: <1987Jul16.234856.6738@gpu.utcs.toronto.edu>
Date: Thu, 16-Jul-87 23:48:56 EDT
Article-I.D.: gpu.1987Jul16.234856.6738
Posted: Thu Jul 16 23:48:56 1987
Date-Received: Sat, 18-Jul-87 09:09:50 EDT
References: <598@neoucom.UUCP> <67@sdeggo.UUCP> <1597@ihuxi.ATT.COM> <1007@unh.cs.cmu.edu>
Reply-To: taras@gpu.utcs.UUCP (T. Pryjma)
Organization: University of Toronto Computing Services
Lines: 49
Keywords: with possible icky results!
Checksum: 05555

In article <1007@unh.cs.cmu.edu> agn@unh.cs.cmu.edu (Andreas Nowatzyk) writes:
# > Sorry, but the protection circuit will be buried deep in one of the LSI's.
# > There will be no way to remove it and even if you could, the notch will
# > still be there on the source CD.  That is what has everyone so up in arms.
# 
# It seems very unlikely that the copy-protection circuitry will be burried
# deep inside. Consider the nature of that chip: several filters, various
# integrators, gain-control, etc. (The block diagram was recently published in
# an audio magazin). This can be implemented either as an switched-capacitor
# device (a) or as a completely digital circuit (a).
# 
Well if you were following the news you would know that the circuit has been
implemented by a US record and entertainment conglomerate, I forget who for the
moment.  The DAT units are going to be sold in two implementations, (1) with
the defeat circuit included and the other without.  The units without the 
defeat circuit will have an empty space where the defeat circuit should have
been if it had been included.

Likewise it should not be all that difficult, for those inclined to do so, to
take the defeat circuit out.  The circuit should also be defeatable by in-
jecting a very low strength 3khz tone into the signal.  Just remeber the 
copy-protection circuit sells for about $1.25 in volume.
# Now for the 10c question: why should a DAT company spend a lot of resources
# on the CP part to do a good job here? After all, they are fighting this
# restriction.
# 

They wont!

# I think that the time it takes a person with EE background to defeat this
# circuit is best measured in minutes.
# 

You do, do you.  I don't, unless the EE was an electronic hack before he knew
what electronics was all about he will probably be all thumbs when he looks
at this thing.

#   --  Andreas


-- 

			 	Taras Pryjma 
				uucp: taras@gpu.utcs
				bitnet: tpryjma@utoronto
				Bell: +1 (416) 536-2821

Ok then, It's settled.  I will have my computer call your computer and work
it all out.  .......   But wait ...... it won't do any good, never mind.