The crew over at Popular Mechanics likes to see what makes a machine tick. Photographer Todd McLellan meticulously took apart GE’s MAC 2000 Electrocardiograph (or EKG) piece by piece, carefully logging and positioning each part neatly to be photographed. It took him 5 hours and 21 minutes to dismantle it, and you can see a video of the process here.
As the article describes, an EKG is a multimeter of the heart. As your heart beats, electrodes on the lead wires pick up the resulting electrical signals from strategic points on your body. These signals are interpreted in three dimensions by a cardiologist—who can literally see your heartbeat.