The fourth edition of this text has been revised and, where necessary, rewritten to incorporate the latest data available in the field of electronics. New material includes an introdcution to flip-flops and counters in relation to digital circuits, a discussion of data sheets and switching operations in conjuction with diodes and transistors and the principles of operation and design of an audio small-signal amplifier. A large number of exercise questions have been brought together in a new section to encourage practical application of the theory presented and aid exam technique and revision. It covers the new BTEC Electronics II course and will also be suitable for advanced CGLI courses in electronics and related studies such as electrical installation. It should also useful for electronics hobbyists or those needing some knowledge of electronics for their work. An ELBS/LPBB edition is available.