🚀 go-pugleaf

In article <1988Jul29.194813.27599@utzoo.uucp>, henry@utzoo.uucp (Henry Spencer) writes:
> In article <1047@unccvax.UUCP> dya@unccvax.UUCP (York David Anthony) writes:

> >	Having transmitted medical images (essentially random
> >data) through every kind of modem known to God, I can with 
> >certainty state that the Telebit Trailblazer does not even achive
> >achieve 9600 bits/sec on random data.  
> 
> You're transmitting with uucp, I assume?  Have you forgotten protocol
> overhead?  (For that matter, have you considered the possibility that
> the CPU is the bottleneck?)

	Bad assumption. I'm transmitting with proprietary hardware
which can keep up with 2.048 mbps serial synchronous data, and 
has DMA access to zero wait-state RAM with 4 mb capacity.

	I never said that the Trailblazer wasn't theoretically 
capable of handling X mb/sec.  What I did say (and using various
methods of very high performance equipment to back it up) is that
when the criteria for a plain old telephone line is satisfied, the
V.xx modems **guarantee** a **specifed** bit error rate and a
**specified** bit stream rate. Period.

	Our customers demand a specified BER at a specified data
rate using random serial synchronous data. Period.  If nothing else,
all someone needs out in Bumfuk, Iowa is a modem which, upon 
adapting to a marginal line, transmits at significantly less than
9600 bps.

	In my application (where I have several lines located in
some major, major, MAJOR markets, say Boston, NY, which can be
used to dial back around to myself, as well as other test setups
in some tiny, tiny, TINY markets of similar ilk) UDS and Rockwell
beats Trailblazer.  The Rockwell R96MD operates error free on
98% of our installations, (in the hundreds) on unconditioned 
residential type circuits, even where the loop loss is very
high (such as Chillicothe, Missouri, or Potomac, Md.). This is
essentially the same OEM modem used by every fax machine manufacturer
on the face of the earth.  In general, the guaranteed BER is
10 e-07. The observed BER is 0. This, with files typically four
meg or more.

	My only transmission overhead is the time it takes to
execute two move.l's to turn on the timer, and turn off the
timer and dump variables containing error counts.  Microseconds,
at worst.  I think my testing protocol is an order of magnitude
more robust than using a Unix box.

	I'm glad that the Trailblazer works for everyone concerned.
All I wanted to call attention to is the fact that 1) QAM does
NOT equal Trailblazer and 2) QAM modems get a bad rap from people
who have installed and operated about a few hundred less than I
have and 3) the Trailblazer statement about bit error rate and
transmission speed is not particularly honest advertising. Now,
if Telebit publishes charts of various line impairments and the
bit error rates (or speeds) which then ensue, I'm all wet.

	But, all I hear is "well, the Trailblazer does 1300 char/sec
(lets assume 8 bit synchronous characters where all the data is
valid and not asynchronous ASCII, or a rate of about 10400 bit/sec)
assming that it is on a good line, or it isn't transmitting anything
in the reverse channel, blah, blah, blah.  I know people have to
do things like this.  There are probably step-by-step metallic
exchanges somewhere where the phone lines are essentially transparent
where the Trailblazer might hit 18,000 bit/sec.  

	My whole point is, is, that the Trailblazer does not 
guarantee a specified data rate at a specified bit error rate.
I can buy a UDS ECC-1 box, too, and get some error rate like one
error every 7 years, too! (This is a packet error correction box
which handles buffering and other junk between the V.xx modem
and the DTE.) We don't use it, BTW. Out of the SIO and into the
modem. What could be simpler?

	Frankly, if you need 100% link availability, you have 
no business using dial-through modems to begin with.  However,
until you have used V.29/V.33 modems, and have an installed data
base (remember, 98 % link availability at 10e-07 BER and the
guaranteed data rate of 9600, 12000 or 14400 bps) of a few
hundred (I lost count at about 275 or so of our customers) please
don't bash 'em. They work quite well. My challenge still stands.


Yours for truth-in-modem-advertising

York David Anthony
DataSpan, Inc.