A cardiac stimulator is described which combines the ease of operation required in clinical investigations, particularly endocavitary studies of cardiac arrhythmias, and the versatility needed in a research context. This instrument uses a microcomputer to control two independent opticully‐isolated Stimulation ports which can be addressed either independently or jointly to stimulate at two different sites. The main software module operates as a cascade of ten real time pulse generators with individually presettable parameters: amplitude, duration, period, initial delay, periodic and cyclic modifiers, triggering mode, etc, A simple interactive procedure allows the operator to define a stimulation protocol either by accessing the generator structure directly, or by calling any of five preprogrammed stimulation protocols. With this combination, the instrument can provide a large variety of pulse patterns. The operator can intervene at any lime during stimulation to change parameter values or modify the pulse pattern. Concurrently with stimulation, the instrument generates time‐codes to help relate car‐dine responses recorded on paper chart and magnetic tope, and reference them to specific events. The instrument can be readily expanded by the addition of parallel microprocessor modules; other real time tasks such as acquisition and processing of cardiac responses can thus be incorporated. Copyright © 1979, Wiley Blackwell. All rights reserved
