HSTnet HST Echo HSTnet 1/0 (813) 394-6488 March 1994
FAQ - Fequently Asked Questions
Q. What is HST
A. HST is a registered trademark of the U.S. Robotics Company (USR). It
was originally used to indicate "High Speed Technology." Before USR
trademarked HST, it was also used by Microcom to describe modem technology.
HST is also the name of the echo that supports users of US Robotics and other
make modems based on that technology. Data Race, Concord, Miracom and others
have licensed HST technology at one time or other.
Q. What is a Courier HST modem?
A. The Courier HST was the first high speed modem released by US Robotics.
Its primary designed transmission speed was 9600bps. The use of HST error
correction increased the maximum transmission speed possible to 11910bps.
Actual maximum speeds were in the vicinity of 11700bps. There have been many
modems that have been called HST. Gradually the modems increased in speed
from 9600 to 14400. The latest version is now 16800 and can be had with
facsimile Class 1 and Class 2.0 depending on model. HST is a unique
assymmetrical channel configuration. MOST of the usable bandwidth is
concentrated in sending data one way at time. Since the vast majority
of data transmission is highly asymmetrical in nature, this has proven a
very efficient transmission method.
Q. What is V.32?
A. The Consultative Committee for International Telephony and Telegraphy
(CCITT) is a body that sets up compatibility recommendations for various
types of electronic equipment. One modem standard set by the CCITT (now known
as the ITU 'International Telecommunications Union') is known as V.32. There
are many ITU specifications that describe modem protocols. The V.32 spec-
ifcation is a 9600 symmetrical protocol that uses MNP for error correction.
V.32bis is a faster version of V.32 and operates at 14400 bps.
Q. What is V.42, V.42bis, Lap-m
A. V.42 is a negotiation protocol for error correcting modems. During the
connection process, the modems tell each other which common and desireable
features are supported by both modems. The modems will select by default the
most efficient error correcting and compression techniques. A more efficient
compression technique than MNP5 is called V.42bis. A more efficient error
correction technique than MNP1-4 is called Lap-m. When V.42 is executed at
the connection phase, it looks for the highest level efficiency both modems
can support. The prefered defaults are Lap-m and V.42bis.
Q. What is a Bler?
A. Bler means Block Error. This is a function of error correction. With
an error correcting modem, any data that fails it's verification check is
Q. What is ARQ?
A. Automatic Resend Request. This is the US Robotics way of labeling the
various error checking protocols. The original HST modem used a proprietary
technique that was similar to MNP and the resulting connect string sent was
9600/ARQ. All USR modems send connect message of ARQ to indicate an error
correcting protocol is detected and in use on both modems.
Q What is MNP?
A. The acronym stands for Microcom Network Protocol. There are different
levels of MNP beginning with level 1. Levels 1 through 4 are in the public
domain and can be used in any software or hardware without paying royalties
to Microcom. The first three levels apply different techniques for sensing
and resending block errors.
Q. How do I order a modem on the USR sysops program?
A. Call the USR company BBS. The number is 708-982-5092. This is the ONLY
way to order a modem on the Sysops program.
Q. What do I have to do to qualify for the Sysops program?
A. First you have to be operating a BBS for at least six months. You
should obtain the latest copy of the Sysops Program offer form USR's BBS.
Then you must be willing to accept the conditions of the Sysop's deal in order
to be considered to receive a modem at the special Sysops pricing.
There are exceptions to this requirement. Owners of the following BBS
software have the waiting period waived.
PC Board Wildcat Power Board
Searchlight Roboboard T.P.Board and Front Door
Remote Access Major BBS First Class
TeleFinder AmiExpress DLG
For details see the Sysdeal.TXT file on USR BBS 708-982-5092
Q. Are there requirements to advertise the modem that I buy as a Sysop?
A. Yes, you are required to operate the BBS and to carry a notice to all
callers that you are using a USR modem, and hopefully which model etc. The
time period of this requirement has typically been six months. See the current
sysdeal.txt file on USR's BBS for precise details.
Q. Why are they so strict?
A. Because many non-sysops have attempted to obtain the special pricing
which they do not deserve.
Q. Why does it take so long to get a USR when I can order other modems and
get them almost immediately.
A. Frequently USR announces new modems when the production lines are not
operating. New modems will have long delays before the first orders are
filled. USR also makes a limited amount of modems available to Sysops, and
these amounts can run out. There is no retail sales department at USR.
They ship on a regular schedule. Other companies sell retail from the factory.
Q. If I can buy a modem direct from other modem makers, why does USR have
such a strict policy?
A. One reason is to protect the distributors and dealers who sell USR
modems. Some companies will sell modems in competition to their dealers and
distributors. Such companies dealers are not likely to view the sysop as a
customer but as a competitor who has taken away profit. Sysops using USR
modems who advertise those modems on their BBS's provide a service that is
likely to benefit USR modem dealers. And such sysops are much more likely to
recieve support from dealers for the advertising the Sysops perform.
Q. What is V.32TERBO?
A. Terbo is NOT a V. Standard. It is a protocol that was developed by AT&T.
It is a version of V.32. The V.32bis version of V.32 encodes more data bits
in a pattern refered to as the Constellation. Several of the "bits" in the
constellation are used to provide a kind of error correction in a technique
known as Trellis Coded Modulation. This is a type of "forward looking" error
correction that adds approximately 2.5 db to the Signal to Noise (S/N) ratio
that a modem required in order to recognize the waveform pattern and its
encoded data bits. Since the telephone lines were found to have enough
bandwidth (frequency width, usually from 300-2700 hz) the V.32bis protocol
was created and will under ideal conditions achieve data transmission rates
of 17100 bps. When line noise occurs errors occur, and the amount of data
bit encoding is reduced. V.32bis has fallback speeds of 12000, 9600 and
7200 bps. This occur as each data bit encoding is dropped, which in turn
allows the use of a narrower bandwidth, increases the effective S/N ratio,
and tend to allow transmission to continue. TERBO, also refered to as
V.32terbo takes several of the data bits in the Constellation that the CCITT
did not think should be used for data, and attempts to use them as data.
Under nearly perfect line conditions the Terbo technique can be used to
transmit as fast as 19200 bps or 21600 in USR terbo. Since the bandwidth
is increased, the sensitivity to noise decreases from 3 to 3.5 db.
Q. What is the fastest modem protocol?
A. Right now, the Telebit Super PEP modem has a carrier rate of 23,000 bps
and can do speeds above 24,000 bps reliably on many more difficult telephone
line conditions than TERBO or V.FC. This is a rating of absolute bit density,
which is how most BBS operators consider speed. If sending of compressed data
is considerd (which is rare on a BBS) then the Hayes V.FC is the current top
speed modem with compressed bit densities of up to 230,000 bps claimed.
Q. Can I upgrade my old HST modem (9600, 14400 or 16800 bps)
A. Yes you can. Several upgrades may be in effect from time to time. One
such upgrade for the very old HST9600 modems is to Dual Standard (9600HST/V.32
9600) for $150. At various times other upgrades or trade in programs are in
effect. The best way to be sure is to call USR.
Q. How do I contact USR directly?
A. You can use a modem to call their BBS at 708-982-5092. The BBS runs a
Total Control rack mount with 8 Courier Dual Standard TERBO modems on it.
There is a section where you can download information on the Sysops program,
products, pictures of modems, and technical tips. There is also a section
taht contains a local USR message area for questions to USR. This is the ONLY
BBS where you can expect to receive an answer from USR technical personnel.
You can also call USR at 800-342-5877 and talk to sales. Or you can call
Technical support at 708-982-5151. Be prepared to wait to talk to anyone as
they are quite busy. USR personnel answer several thousands of questions per
Q. If I prepay will I get my modem sooner?
A. Probably not. There have been several instances where modems were
prepaid and arrived after months of waiting. I don't recommend prepayment,
unless by credit card, and only if the shipping date is soon and promised.
Then if the modem does not arrive on time, the charge can be cancelled and
refused at your bank.
Q. Is the Courier modem really upgradable? How is this done?
A. In the past all modems were made to do one thing at one speed. For the
past several years, modem technology has improved so rapidly that the ONLY way
to ensure a modem could be upgradable was to make sure the processors could be
changed as needed. USR Courier modems have all the necessary parts to perform
the modem protocol functions on a small seperate printed circuit board that
can be replaced with more powerful processors as needed.
Many modem buyers were highly disappointed after having purchased a bargain
modem to find out that a newer modem was now available that was 50% or more
faster, or more robust. Some current modem makers are providing very powerful
modems, but sending them out with slow speed protocols in them. Then those
buyers are required to download the higher speeds protocols and run a program
to "upgrade" their modems. (Why not just ship them ready to run at high
speed?) This makes such modem less competitive as they have to be priced
comparable to slower modems, even though built with the processors of the