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From: caf@omen.UUCP (Chuck Forsberg WA7KGX)
Newsgroups: comp.dcom.modems
Subject: Re: > 9600 bps over conditioned leased lines?
Message-ID: <418@omen.UUCP>
Date: Fri, 14-Nov-86 04:05:25 EST
Article-I.D.: omen.418
Posted: Fri Nov 14 04:05:25 1986
Date-Received: Sun, 16-Nov-86 20:18:09 EST
References: <28@halleys.UUCP> <2942@cbosgd.ATT.COM> <464@brl-sem.ARPA>
Reply-To: caf@.UUCP (PUT YOUR NAME HERE)
Organization: Omen Technology, Portland
Lines: 30
Keywords: recurring costs

In article <464@brl-sem.ARPA> ron@brl-sem.ARPA (Ron Natalie <ron>) writes:
:In article <2942@cbosgd.ATT.COM>, mark@cbosgd.ATT.COM (Mark Horton) writes:
:> I haven't followed it closely, but yesterday a salesperson pointed
:> at a TeleByte modem, said the cost was $3500 each, and that it did
:> 19.2K over regular dialup lines.  Part of this is probably done with
:> data compression, so it may not help your application.
:
:Once again, as pointed out before, some of these cheap and slick data
:compressed/error corrected modems are pretty atrocious.  The Telebyte
:for instance is damn near unusuable for either normal UNIX use or UUCP
:as it is really half duplex and takes forever to turn the line around.

Unusable with unsuitable protocols, but not unusable!  DCA recently
tested Pro-YAM's public domain ZMODEM protocol with a pair of their
TrailBlazer modems, and obtained a throughput of about 14,000 bps (a
record, comfortably surpassing "Crosstalk-FAST").  ZMODEM, it happens,
is ideal for these modems because the receiver does not have to
acknowledge every transmitted block, only to send error packets when
necessary.  Of course, even ZMODEM will be slowed if one must send many
itty bitty short files, but this is not the usual case. 

For more information, look at the ZMODEM protocol description sent over
net.sources some time ago, available in ZMODEM.ARC on Telegodzilla.

Chuck Forsberg WA7KGX Author of Pro-YAM communications Tools for PCDOS and Unix
...!tektronix!reed!omen!caf  Omen Technology Inc "The High Reliability Software"
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