Held provides a clear and complete guide to modems and related subjects. He begins by discussing serial transmission, then explains the differences between digital and analog transmission and introduces the role of the modem. He discusses every aspect of modems, from the legal requirements of the FCC through the technical aspects of modulation standards, up to and including V.29, V.32, and V.33.

The discussion of the Hayes command set and variations is thorough. The sections on error detection and correction and on data compression (including MNP) are good. A chapter presents the detailed specifications of eight popular modems, followed by a discussion of compatibility issues. One chapter is devoted to modem status indicators and troubleshooting techniques. Another chapter presents 25 modem parameters as a checklist to be used when purchasing a modem.

This book is well written. My only complaint is in regard to the handling of the term, “protocol spoofing.” The phrase is used several times, but it is not until the last use, 30 pages after the first, that the phrase is clearly defined.