Electroconvulsive therapy (ECT) is a long established form of treatment for specific, serious mental disorders, but one which is still surrounded by much misunderstanding and fear. The use of electrical current administered to the brain to ‘treat’ illness remains a barbaric concept to many people. Much research has been conducted to establish the efficacy of ECT, which is now widely accepted. However, the working principles of the ECT machine itself are little understood, and more research remains to be done to establish, more scientifically, which is the ‘best’ way to administer the electrical stimulus. With the recent introduction of the concept of “stimulus dosing” (for a review see Lock, 1994), the need to be aware of the ECT machines available and their abilities and limitations is important.