Electrocardiograph. Computer screen display of electrocardiograph readouts received by telephone. The electrocardiograph records the electrical activity of the heart; the vertical axis represents the electric potential of the heart whilst the horizontal axis represents time. The electrocardiograph reading can be analysed to reveal any potential heart problems. These electrocardiographs have been recorded by a portable device, known as a card guard", before being sent to the hospital by telephone. This allows patients to lead a normal life whilst still having their condition monitored regularly."