 The magazine of the Melbourne PC User Group Driving Modems Major Keary |
 |
The modem is likely to be the second most common add-on (after a printer) acquired by computer users; it is often the source of most frustration and requests for assistance.
There is a plethora of makes and models and their cost, particularly for low-end equipment, has dropped considerably. For a small price differential it is possible to have fax as well as data facilities in the one unit.
Standard fax machines operate at 9600 bps, so there is not much point in buying one with a higher rating unless you are communicating with a fast fax/modem. Current fax/modem equipment generally presents both facilities at the same speed. Thus, a 14,400 bps fax/modem is likely to operate at that speed in both modes. However, that is not universal and some equipment has two different speed ratings, one for each mode. The moral is, read the fine print.
Just about any fax machine has the capacity to compress the data stream when sending, and to uncompress data in receive mode. Most modems also now have built-in compression.
Having built-in compression is not much help if the machine at the other end of the line doesn't know about that kind of thing. Modems and fax machines are pretty smart, however, and have a little chat to each other before any data is sent. The result is that the most sophisticated equipment drops back to the capability of the less-endowed machine.
The things to look for are MNP-5, and V 42bis. MNP stands for Microcom Networking Protocol and MNP-5 is a compression algorithm that uses dynamic Huffman coding. The CCITT (now ITU-T) established an international standard, known generally as V 42bis, based on the LZW algorithm and which is more efficient. Look for both MNP-5 and V.42bis in the specifications (and among the how-good-I-am claims on the packaging) of any modem you may consider buying. MNP-5 is not as efficient as V42bis. The "bis" means a second version - it comes from the French.
Incidentally, V.42 is not the same as V.42bis; the former is a standard protocol for error control, the second version of the standard includes data compression. On 28,800 bps equipment you may see UFC; unless something has happened recently it is not an ITU-T standard, but is a Rockwell/Hayes designation for a high speed transmission protocol. It will become a standard, but these things take time.
How Fast?
For BBS users the important speed rating is that of the modem. Some fancy figures are often given as a "port speed" on the assumption that the modem is dealing with an uncompressed data stream. They arrive at their very high port speed by using both the bps rating and compression ratio as factors.
If the data has already been compressed, then the modem's compression utility, if active, will make hardly any difference in fact it could slow down transmission by attempting to compress data that just won't compress any more.
Getting Help
Turning to Dial Help is not always the most effective way to go about choosing a modem. There are many factors that the would-be purchaser has to assess before someone else's opinion can be meaningful.
First-time buyers need to arm themselves with information, and those considering an upgrade would be wise to revise their knowledge. There are a number of books about modems, but many are pitched at the North American market and use a lot of space describing online services not available to Australian users.
When looking at modem books check the contents for references to Delphi, America Online, GEnie, and Prodigy. If a book devotes a lot of space to describing such services it may be of doubtful value.
When assessing a book's suitability take into account the main use you will have for a modem. That, of course, also goes for your choice of modem-but if you want information to help with that decision the book will come first.
Don't let yourself be carried away by what appears to be some marvellous software that comes with a book. It is common to offer book-with-disk packages, but in many cases their value is doubtful. There are some gems, but not many. To help you choose, here are some I have looked at.
Modems for Dummies
Moderately priced ($39.95) it is in the style of the Dummies series: light-hearted, non-technical language, and plenty of useful tips.
Almost a third of the book is given over to describing North American online services, information of marginal value to Australian readers. A chapter on CompuServe may be of some interest, but subscribers get pretty good documentation direct.
A chapter on the Internet is an easy introduction if you are interested in getting a connection. Introduction is the operative word-don't expect to become a black belt user.
The main part of Modems for Dummies is a down-to-earth description of how modems work, how they communicate, things you can do, and the trouble you can get into.
There are excellent illustrations of equipment, cables, plugs, and so on. Any novice should be able to install a modem, internal of external, with a minimum of difficulty. The COM ports are explained, communications software is described in general, and there are some cautions and tips about online services in general.
The book makes good use of question-and-answer format to cover modem software and hardware. The material is well organised and provides comprehensive information that novice (and even experienced) users require. That format is carried over into troubleshooting sections with good effect and does not overlook the simple, but common problems. For example, "My software says it can't find a CTS signal"; answer: "Turn on your modem".
The ten most commonly-used AT commands are described, which should be sufficient to enable users to decipher the full set in a user manual.
Protocols (Zmodem and the like), downloading, uploading, host mode, and using ordinary BBSs are all explained to a level suitable to get a new user online. There is also advice about buying a modem - internal or external, and other considerations - and an explanation of all those lights.
It is one of those books that is designed to become redundant in a short period of time-the material is easy to absorb and any new user should soon either be at a level of competence sufficient for all of his or her needs, or be looking for something more technical. It provides the leg-up that all new users need.
|
Tina Rathbone: Modems for Dummies ISBN 1 56884 001 2 Published by IDG Books RRP $39.95 |
New Riders' Guide to Modems
Also for beginners, NR's Guide takes readers through to a more advanced level. At $43.95 it is worth looking at, particularly if you intend using
HyperACCESS for Windows as your communications software.
A disk comes with the book and includes a test drive version of HyperACCESS -
it is crippled, but implemented sufficiently for evaluation. The book's examples of modem operation use the DOS version of that package. The Windows version requires over 3 MB of hard disk space.
There is minimal space given to describing online services (Prodigy etc.), which is good for local users who don't need that information. A chapter on the Internet gives a pretty good coverage of the various services.
Most of the book is about choosing, installing, and using a modem. The information is well presented and includes settings under OS/2.
The important AT commands are listed and there is a useful glossary of communications terms that includes the relevant CCITT standards. A brief chapter covers fax and there is a good troubleshooting section on Windows comms software.
It is a good guide for anyone intending to buy a modem for the first time.
|
Schindler: New Riders' Guide to Modems ISBN 1 56205 302 7 Published by New Riders 369 pages + disk RRP $43.95 |
The Modem Reference
Even though about a quarter of the space is given to describing commercial services, this is a benchmark text by which others will be measured. It deserves a place in any library as a useful resource for all levels of communications users.
A chapter on telecomputing - communication via computer-in all its aspects is followed by a technical
description of how communication by modem works. While there is an assumption that the reader is computer literate, the language is plain and easy to understand. It provides a very good background that may well make the reader more knowledgeable.
A chapter on comms software is useful in that it discusses the kinds of features a good program should have. The follows detailed descriptions of modem use-moving files, using BBSs, and commercial services.
Two chapters of particular interest cover on-the-road communications, and Windows applications. The latter addresses a number of issues that face those who want to run comms programs through Windows.
Troubleshooting, technical stuff about wiring, and keeping clear of viruses are all dealt with and there is a disk some useful files. The disk has script files for use with the DOS and Windows versions of ProComm, compression utilities, a selection of comms programs including
Odyssey, WinZip, and batch files.
|
Michael Banks:
The Modem Reference 3rd edn. ISBN 1 56685 027 X Published by Brady 815 pages + disk RRP $59.95 |
Reprinted from the November 1994 issue of PC Update, the magazine of Melbourne PC User Group, Australia
