Much like standard electrocardiography (EKG), the Holter monitor records electrical signals from the heart via a series of electrodes attached to the chest. The number and position of electrodes varies by model, but most Holter monitors employ from three to six. These electrodes are connected to a small piece of equipment that is attached to the patient's belt, and is responsible for keeping a log of the heart's electrical activity throughout the recording period.
In addition to receiving the device itself, most patients are also asked to keep a diary of activities, symptoms, and times that an arrhythmia occurs. This information is used by doctors and technicians to rapidly pinpoint problem areas in the vast amount of data recorded during the monitoring period.