MODULAR ELECTROCARDIOGRAM DEVICE WITH LIMB-LEADS AND EXPANDABLE CHEST-LEADS

A data acquisition system for use with expandable ECG electrode systems. The data acquisition system includes a main unit and one or more expansion units for increasing the number of ECG leads applied to a patient for enhanced monitoring capabilities. Multiple embodiments are illustrated for providing a common mode signal between the main electrode unit and expansion units without requiring the physical transmission of voltage potential between the main unit and the expansion unit. In one embodiment, the main unit and the expansion unit share a common ground reference potential. In a second embodiment, an optical signal is transmitted between the main unit and the extension unit to relay the common mode information while in a third embodiment, common electrode potentials are provided to both the main unit and the extension unit for constructing their own common reference signal.