Portable electrocardiograph. Portable electro- cardiograph (white, at upper left) sending data by telephone to a central, hospital computer for analysis. The electrocardiograph monitors the electrical activity of the heart using a number of electrodes (lower frame). The electrocardiograph reading can be analysed to reveal any potential heart problems. This device, known as a card guard", allows patients to lead a normal life whilst still having their condition monitored regularly."