Evaluation: single-channel electrocardiographs.
D004553:Electric Conductivity; D004560:Electricity; D004562:Electrocardiography / Q000266:history / Q000295:instrumentation*; D004865:Equipment and Supplies, Hospital / Q000592:standards*; D005060:Europe; D005069:Evaluation Studies as Topic; D049672:History, 19th Century; D049673:History, 20th Century; D006801:Humans; D014481:United States