An electrocardiogram (ECG) extension cable includes a first connector configured to be electrically coupled to a physiological monitoring device, a second connector configured to be electrically coupled to an ECG lead set including a processor, an input/output (I/O) wire configured to transmit data between the physiological monitoring device and the processor, a ground wire that establishes a ground path between the first connector and the second connector, a series protection element coupled in series along the ground wire, a bypass path coupled to the ground wire in parallel to the series protection element, and a switching element arranged along the bypass path and configured to redirect the ground path along the bypass path, thereby bypassing the series protection element.