Path: utzoo!utgpu!water!watmath!clyde!rutgers!mit-eddie!uw-beaver!fluke!jeff
From: jeff@tc.fluke.COM (Jeff Stearns)
Newsgroups: comp.dcom.modems
Subject: Re: Telebit -- thanks
Message-ID: <2905@fluke.COM>
Date: 17 Feb 88 21:05:50 GMT
References: <626@ddsw1.UUCP> <4560002@hpihoah.HP.COM> <1004@neoucom.UUCP>
Sender: news@tc.fluke.COM
Organization: John Fluke Mfg. Co., Inc., Everett, WA
Lines: 46

In article <1004@neoucom.UUCP> wtm@neoucom.UUCP (Bill Mayhew) writes:
> It is true that both the Telebit Trailblazer and the Courier HST
> provide up 19.2K bps host interfaces. ...  The trellis coding used
> in the Trailblazer is also different, in that the fallback on poor
> lines is incremental in much smaller bps steps than the HST.
>
> Over the next few weeks, I plan to wring-out both the Telebit
> Trailblazer and the HST...

I've installed a pair of Trailblazers and studied them fairly closely for
several weeks.  They are true champions when speaking PEP to one of their
kind.

HOWEVER, they are tepid performers at 1200 and 2400 baud.  This shows up
most dramatically when the line levels are low or noisy.

Our UUCP connection to an overseas office just plain broke when we replaced
our UDS modems with Trailblazers.  Uucico would timeout and re-ack so badly
that throughput was abysmal.  Often the phone connection would break within
the first minute.  Days went by without a single successful file transfer.

Immediately after restoring the UDS modem, we exchanged over a hundred files
without a single hiccup.

This isn't an isolated event.  We use a cut-rate long-distance carrier to carry
our calls to the Bay Area; the UDS modems could usually handle them adequately
at both 1200 and 2400 baud.  The Trailblazers simply cannot.  Transmissions are
so garbled that one can barely recognize that the destination computer is
running at the proper baud!  

(I've experimented with other carriers; it's true that ATT offers superior
service.  The Trailblazers work well when the long-distance call is carried by
ATT.  Unfortunately, it's not a viable option for us right now.)

In summary, I find that Trailblazers are superb modems when speaking PEP or
communicating at low speeds over clean, quiet lines.  However, they are
poor performers at 1200 and 2400 baud over suboptimal connections.

Final word: My Trailblazers have firmware rev "BA3.01".  Telebit tells me that
release 4.0 may improve performance at 2400 baud.
-- 
	    Jeff Stearns
    Domain: jeff@tc.fluke.COM
     Voice: +1 206 356 5064
      UUCP: {uw-beaver,decvax!microsof,ucbvax!lbl-csam,allegra,sun}!fluke!jeff
     Snail: John Fluke Mfg. Co. / P.O. Box C9090 / Everett WA  98206