This is the introduction to PLCs for which baffled students, technicians and managers have been waiting. In this straightforward guide Bill Bolton has kept the maths to a minimum, avoided detailed programming instructions and presented the subject in a way that is not device-specific. Having read this book you should be able to: * Identify the main design characteristics and internal architecture of PLCs * Describe and identify the characteristics of commonly used input and output devices * Explain the processing of inputs and outputs by PLCs * Describe communication links involved with control systems * Develop ladder programs for the logic functions AND, OR, NOR, NAND, NOT and XOR * Develop ladder programs involving internal relays, timers, counters, shift registers, sequencers and data handling * Identify methods used for testing and debugging Ideal as an accessible introduction for university students, the second edition includes expanded sections on internal architecture, input-output devices, networks, and programming languages with microprocessor systems, and has been fully revised in line with the new BTEC Higher National unit on PLCs, and the 2000 specifications for the Advanced GNVQ unit from Edexcel. A clear and concise introduction for students, technicians, engineers and managers Ideal for BTEC National, HNC, HND and first-year degree modules Revised in line with the new BTEC Higher National unit on PLCs and the 2000 revision of the Advanced GNVQ unit (now an optional unit)