Abstract: An instrument for detecting and measuring various characteristics of cardiac pacers and electrodes and visually displaying such measurements selectively on a digital display includes pacer analyzer means for measuring and displaying characteristics of a pacer, such as rate, pulse width, peak voltage and trailing edge voltage, electrode analyzing means for measuring and displaying characteristics of an installed electrode, such as impedance and intrinsic and evoked R-wave voltages and internal pacer means including means for adjusting pacer impulse rate and voltage and means for measuring and displaying various pacer characteristics of the internal pacer impulses, such as rate, voltage and amperage, a rechargeable battery for energizing the various circuits of the instrument and means for preventing externally supplied battery recharging electric power from communicating through the instrument with installed cardiac electrodes and with a pacer to be tested.