The document discusses the electrocardiograph (ECG), which records the electrical activity of the heart in a graphic form called an electrocardiogram. It describes the ECG's medical applications in checking heart rhythm, axis, and muscle state. The major components and operating principle are also discussed. Advantages include being noninvasive, inexpensive, and useful for detecting latent cardiac conditions. Disadvantages include sometimes being normal despite serious problems. The document outlines current design improvements and contributions of ECGs to easier heart monitoring.