Each component of a pacemaker system is a potential weak link in the pacing chain. Whether or not pacing failure is caused by battery depletion or by electrode fracture, these malfunctions can be diagnosed with the help of intermittent and regular transtelephonic surveillance. Sufficiently large numbers of patients enrolled in such surveillance systems enable the early identification of faulty pacers and leads and alert the medical community against their use. Indeed, the pacemaker surveillance systems in operation at present form the cornerstone of defense against pacemaker malfunction emergencies.