Jonathan Ward is an independent software developer in Dallas, Texas. He may be reached at (214) 248-7694.
For information on acquiring books reviewed here, contact The C Users' Bookstore. (913) 841-1631.
The first portion of The Complete Modem Reference discusses modem connection and the current modulation methods and standards. Later chapters include "intelligent" modem features (like the Hayes AT command set and error detection and data compression) as well as descriptions of several popular modems, a modem-buyer's feature guide, and a chapter on testing modem operation.
The introduction explains why modems are used and what they do. It also covers many communication basics, such as baud, parity, and full/half duplex. The introduction is really geared to the novice but can provide a refresher for those of us who take modem communications for granted. It discusses modem-to-PC connection in great detail. It devotes several pages to installing an internal modem or serial I/O card into a PC. I would hope that this kind of instruction comes with the modem documentation, but you can never be too sure.
The chapters on modulation methods and current modulation standards describe the different methods that modems use to modulate a signal on the phone lines, as well as the accepted Bell System and CCITT standards. Limitations of the phone line are described followed by descriptions of modulation methods such as FSK (frequency-shift keying), PSK (phase-shift keying), QAM (quadrature amplitude modulation), and trellis coding. Descriptions of modulation standards include Bell 103 (300 baud), Bell 212A (1200 baud), V.22bis (2400 baud), and V.32 (9600 baud) which are the most popular and widespread. A table is included characterizing all of the modulation standards I've ever seen plus a half dozen or so. Each of these is also discussed in detail.
No modem reference would be complete without a description of the Hayes AT command set. The Hayes command set is the standard around which most all other modem command sets are based. The description of the command set is thorough. The basic and extended commands are described. Most of these are included on other brands of modems. Error detection and correction are important modem topics and are well handled. Descriptions of MNP and V.42 error correcting protocols are clear and easy to understand. Data compression techniques like MNP level 5, MNP level 7,and V.42bis are all included.
An overview and a feature comparison of several popular modems although now current may or may not age well. Emerging modem technology and time will tell. There is no real comparison of modem operation under adverse conditions, no throughput testing, and no comparison of the data compression techniques. The reader would be better served by referring to one of the magazines that performs modem comparisons on a regular basis. The chapter on criteria for modem selection is quite detailed. This information, when combined with current reviews should prove to be quite useful in selecting a modem.
Techniques for testing the modem operation include internal diagnostics, self tests, and digital and analog loopback tests. These are given more treatment here than you may find in most modem documentation. The section on modem testing also includes descriptions of the modem indicator lights.
One subject that was excluded from the book was the communications program. Once you have a modem, the next most important piece of "equipment" you need is a good communications program. This is the software that lets you use the modem to call other modems and transfer files. Also, there was no real description of the information services that are available to modem users other than a brief mention. Major bulletin boards were not mentioned at all. It is assumed that the reader knows what to do when he has a modem.
This book has something for everyone from the novice to the advanced user. The novice would be best served by the introduction and chapters on modem operation, popular modems, and modem features. The advanced user will find a compilation of modulation techniques and standards as well as lengthy descriptions of the error detection and correction as well as data compression. I found that I already had most of the information in this text spread across three or four other references. However, this is one reference that contains it all. If you are looking for a general modem reference, this is it.
The Complete Modem Reference
Gilbert Held
Wiley and Sons, 1991
ISBN: 0-471-52911-7