Path: utzoo!utgpu!water!watmath!clyde!burl!codas!mtune!mtgzz!drutx!dvac
From: dvac@drutx.ATT.COM (VachonD)
Newsgroups: comp.sys.apple
Subject: Re: 2400 baud modem
Message-ID: <6409@drutx.ATT.COM>
Date: 12 Jan 88 17:34:17 GMT
References: <8801062035.aa29520@SMOKE.BRL.ARPA>
Organization: AT&T, Denver, CO
Lines: 60


Well, before you go spend $200 on a 2400 Baud modem, you may want to think 
about holding off and getting the latest modem from US Robotics.  The
USR 9600 HST.  This modem is really I nice piece of hardware, and word is
that USR is looking on putting out a new set of ROMS for the modem soon that
allow it to go faster than 9600 Baud.   

It uses a technique called Trellis Coded Modulation for the transmission of
data.  The modem has a built in buffer which takes a bit of wait time off
of your computer (especially if you run a BBS).  The modem supports automatic
fallback to lower baud rates, 300 and 1200 (Bell Standards), and 2400 (CCITT
standard).  Since 9600 has no standard yet (as far as CCITT is concerned), 
US Robotics last year offered a sysop support program to try and get a lot of
their modems out in the field.  The modem was being sold to BBS System Operators
for $495 + Shipping ($505).  I just ordered one for my BBS on 12/31/87...the
last day for the offer.   

You can get the modem from mail order houses for around $650-$700.  If you do 
a fair amount of long distance calling of other BBS's (like I do) , you will
make up for the savings real quick.  Look at it this way...  Let's say you have
a 4000 Block Prodos File....(Some Apple II GS software is that length)

300 Baud......5+ Hours
1200 Baud.....1 1/2 Hours
2400 Baud.....3/4 hour
9600 Baud.....15 minutes

When you are paying for a long distance call during that time, you can see the
savings you end up with.  Look at a 250 Block file....(Average Apple II/e/c
file length)...

300 Baud......1 Hour
1200 Baud.....20 minutes
2400 Baud.....13 minutes
9600 Baud.....5 Minutes

These are all approximate or calculated times, but are pretty close....

As you can see if you do a lot of long distance data transfers it doesn't take
long to make your money back.

The USR HST 9600 is made for regular phone lines because it uses 9600 baud in
one direction and 300 baud in the other.  The reason for this is that most
BBS/System operations are interactive and 300 baud is for the most part, fast
enough since most people can only type that fast.  For High Speed Data transfer
type connections, this setup is great since the sending station can send at
9600 while ACK's or NAK's are sent at 300 in the return direction.  

The reason USR did this is to reduce the amount of tone overlap, and line 
noise while increasing data integrity and error occurrence.  The USR HST 9600
baud uses priority sending which determines which end of the
connection has the most data to send, and will flip/flop the 9600 baud lead
to that direction.

I have some files that explain the HST and it's technical aspects.  If people
would be interested in these, I could upload them to the net, or I could 
just e-mail them to those who want it.  Or you can get the files yourself from
the US Robotis Run Ubu Run BBS at 312-982-5092.

Later -=> Dan Vachon <=-        !ucbvax!ihnp4!drutx!dvac