Controlled voltages for electroconvulsive therapy

A description is given for the design of an isolated output, servo-controlled voltage, electroconvulsive therapy (ECT) machine for the safe, controlled application of 60-Hz alternating current (ac) signals between 0 and 230 V rms for controlled periods ranging from 0.1 to 2 sec. Added safety is provided by current limiting in the range of 360 to 770 mA rms for patient impedances ranging from 500 to 50 omega. The use of this equipment has permitted a detailed description of the impedances characteristic of unilateral ECT.