This book assumes that you have a passing acquaintance wilh electrical or electronic circuits. This may come from formal study of basic electronic components (for instance, do you know what resistors and capacitors are, and how they react to electrical stimulation) and network analysis (for instance, do you recall Kirchhoff's laws). Or perhaps you picked up a working knowledge from your job, or as a hobby. If you have a circuit whose operation you basically understand, and you want to simulate this circuit to check the details of operation, you probably know enough to understand PSpice.