Ten chapters and an extensive glossary make up this book. I found the PBX coverage disappointing. The author is behind the times and in many cases wrong in his analysis. When he speaks of data protocols, he is on firmer ground, but the analysis is shallow and incomplete. The present edition of the book reflects its antecedents. It makes many references to the AT&T (Bell) System. Six or seven years after the AT&T divestiture, the author should be more careful. On page 282 he claims AT&T “is leading the ISDN effort,” a claim that even AT&T would make with caution.

The author purports to show the reader “how to…determine system requirements and perform design trade-offs between various technologies, such as PBX, baseband and broadband.” He is not qualified to make such an assertion. On page 2, he says, “The public telephone circuits are designed for voice service, and have limited data-carrying capabilities. The error rate on telephone lines can often exceed 10,000 times that expected on direct links.” The error rates on modern PBXs (certainly those involved in any tradeoff) are remarkably close to the error rate of direct links, and both are becoming vanishingly small. (Error rates of 10^-11 to 10^-13 will become common in the near future.) The author’s lack of understanding of switching theory is revealed on page 8 where he says:

Space switches are arranged to connect a number of inputs (N) and outputs (M). If a single space switching network is to provide simultaneous connections between each input and any available output, a matrix of N × M switching elements is needed. Thus to connect 200 users to any of 200 devices would require 40,000 bi-directional switching elements.

This statement is wrong. The author states a nonblocking condition, but in fact the 40,000 elements he refers to allow for all 200 inputs to be connected to all 200 outputs simultaneously. To connect 200 inputs to 200 outputs requires only that 200 paths through the network be guaranteed and that all input and output ports have full access to the paths. While the design of a nonblocking matrix is a complex task, many designs have been constructed. One company offers a nonblocking switch with 16,000 input and output ports in half a shelf of equipment.

This book is at its best when describing the relationship among various standards and the consequent protocols. It needs to be thoroughly updated to reflect the 1990s. It offers no discussion of SONET or FDDI. The definition of fiber optics in the glossary gives three impressions: fiber is a “direct replacement for conventional coaxial cable and wire parts,” glass takes less physical space, and fiber is immune to electrical interference. Nothing is said about the enormous bandwidth, low loss, and low error rate of fiber optic systems. Also, nobody should be left with the impression that fiber is a “direct replacement” for coax and wire.

I cannot recommend this book.