In October 2001 the Open University introduces a new modular programme for initial teacher training for secondary teaching. Four set books will develop and extend the required subject knowledge for the National Curriculum in Design and Technology. Although intended for initial students many existing teachers will find these up to the minute texts invaluable updates on the statutory requirements of subject audits. All include practical and theoretical activities for readers to undertake and questions for them to answer. This book covers aspects of subject knowledge relating to: inputs and outputs in systems; feedback; introduction to circuits; transistors, resistors and capacitors. The main focus is an digital systems, but reference is also made to analogue systems. There is also a focus on electronic and computer-based systems, but reference is also made to pneumatic, hydraulic and mechanical systems.