Direct-writing color vectorcardiograph

By employing a specially designed instrument, a "color vectorcardiogram," a single, colored horizontal plane vectorcardiogram (VCG) was written directly on the recording paper. At first, the voltage in the X, Y and Z axes was memorized into the digital memory cells. After that, the voltage in the X and Z axes was slowly read out so that a horizontal plane vectorcardiogram was written directly on the paper of the X-Y recorder. The color of the recording pen varied according to the voltage in the Y axis, which was read out simultaneously with the voltage in the X and Z axes.