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Path: utzoo!watmath!clyde!bonnie!akgua!whuxlm!harpo!decvax!ittvax!dcdwest!sdcsvax!sdcrdcf!darrelj
From: darrelj@sdcrdcf.UUCP (Darrel VanBuer)
Newsgroups: net.micro
Subject: Re: Re: 1200 buad modem designs wanted
Message-ID: <1494@sdcrdcf.UUCP>
Date: Mon, 26-Nov-84 10:06:00 EST
Article-I.D.: sdcrdcf.1494
Posted: Mon Nov 26 10:06:00 1984
Date-Received: Wed, 28-Nov-84 02:36:54 EST
References: <4660@fortune.UUCP> <4400078@uiucdcsb.UUCP>
Reply-To: darrelj@sdcrdcf.UUCP (Darrel VanBuer)
Organization: System Development Corp. R+D, Santa Monica
Lines: 30
Summary: 


The main reasons you can buy $10 phones but $100 interfaces (DAAs):
1)  DAAs have several relays rather than cheap molded switches
2)  The phone is self-contained.  As a result, max output can be done as a
byproduct of design (e.g. microphone saturates below limit).  Required
isolation from power lines done by 1/16 inch of plastic shell, etc.
An unrestricted DAA has to deal with some fool connecting 110V AC or a 100 W
audio output stage to line, and still achieve isolation (until it melts
down).
3)  Mass production.  DAAs are a specialty item, mostly holdovers from when
the phone company was paranoid or predatory about what you connect.  Modems
made in any quantity have it designed in as another $10 or $20 feature.
Darrel J. Van Buer, PhD
System Development Corp.
2500 Colorado Ave
Santa Monica, CA 90406
(213)820-4111 x5449
...{allegra,burdvax,cbosgd,hplabs,ihnp4,orstcs,sdcsvax,ucla-cs,akgua}
                                                            !sdcrdcf!darrelj
VANBUER@USC-ECL.ARPA

-- 
Darrel J. Van Buer, PhD
System Development Corp.
2500 Colorado Ave
Santa Monica, CA 90406
(213)820-4111 x5449
...{allegra,burdvax,cbosgd,hplabs,ihnp4,orstcs,sdcsvax,ucla-cs,akgua}
                                                            !sdcrdcf!darrelj
VANBUER@USC-ECL.ARPA