Unlike almost all books on analogue filters, this text does not contain a single mathematical formula. Yet, one can use this book to design useful filters whose behavior is described by complex differential equations or transfer functions. The paradox is resolved easily--all the mathematical models and solutions are hidden inside computer programs (written in GW BASIC) that accompany each chapter. Every time the author introduces a new type of filter, the corresponding circuit diagram and a program calculating its components assist his discussion. Along with the programs one finds comments, which are deliberately separate from the program text (to save both memory and execution time for this interpreted language). The diskette attached to the book contains all the BASIC sources for these programs, which should run on any IBM PC or compatible computer.

The author, an electronics hobbyist, has aimed the book at a similar audience, those who would like to quickly understand how filters work and can be built, without much theory. The book would also be useful for technicians.

For more mathematically sound reading, the book refers to some more comprehensive sources, including Zverev [1]. The author quotes some tables from Zverev’s catalogue as well as from Saal and Ulrich [2].

After a brief introduction to filters, outlining why and where filters are needed, how they generally work, and what the limitations of simple filters are, the book heads off into the set of major filter types (passive, active, and switched capacitor). These include Butterworth filters, Chebyshev filters, elliptic filters, Antoniou filters, inverse Chebyshev filters, Linkwitz filters, Lipshitz filters, Bessel filters, and notch filters. The author covers Antoniou’s generalized immittance converter and a series of devices based on it, such as gyrators and negative resistors. Each chapter summarizes the major qualities of the filter discussed.

The book is definitely written in a practical way, with many useful tips to engineers who are building filters for various applications. The reader should regard the author’s intentions of programming efficiently with some reservations. Despite all such intentions, in the very first example of a program in BASIC on page xi, he shows an inefficient way of programming an iterative loop: “199 FOR I=1 TO 101: F=FSTART+(I-1)*S.” Obviously, even most modern computers would need longer to calculate a product than a sum. I would definitely recommend using the partial sum technique for calculating F rather than always computing it from FSTART.