Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!lll-tis!lll-winken!scooter!neoucom!wtm
From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: comp.dcom.modems
Subject: Re: Which is best?
Summary: Defending both HST and the Trailblazer
Message-ID: <1383@neoucom.UUCP>
Date: 26 Oct 88 21:47:25 GMT
References: <9515@conexch.UUCP> <2590@sultra.UUCP> <23328@amdcad.AMD.COM>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 29


I've used both of these modems.  Both are very good units.  Both
are very well constructed.  Both offer excellent noise rejection
characteristics.

The main difference is that the Trailblazer modem through the use
of its internal uucp ACK generation achieves transfer rates that
average around 1100 char/sec between our site here in Ohio and
scooter in California.  The USR modem was limited by the fact that
it the 300 bps allocated to the reverse channel is not enough to
transmit the ACK within the minimum time.  The trailblazer can also
in effect ACK the packet before it has actually reached the other
end, ensuring continuous filling of the xmit buffer.  With the USR
modem you have to eat the turnaround time of the other host + line
turn around (not modem turn around, since the reverse channel is
already available).  A long distance call might have about 50 mS
delay; add to that whatever the overhead of the other host is.  Our
uucp transfers over a good quality phone line with the USR ran
about 450 - 500 char/sec.

The icing on the cake is the internal compression in the TB+.

The one place that USR whips the Trailblazer is cost, but that
margin has been cut back with the recent introcution of the Telebit
Junior (my name for it), model T1000.

The people on the FIDO network are just about as religious about
USR modems as we Unix denizens are about Trailblazers.

--Bill