Editorial

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Abstract
The reduction in amplitude of QRS signals due to inadequate high frequency response of direct writing electrocardiographs was studied by recording precordial ecgs on magnetic tape and playing them back into 18 direct writers. Nine instruments showed root-mean-square errors exceeding 11% and in some cases signals had to be increased by 50% to reach their true value. Sixteen direct writers failed to meet the minimum requirements of the American Medical Association. Correlation with frequency response indicated that direct writers should maintain a cutoff frequency of at least 100 cps.