A patient monitoring system includes a plurality of leads adapted to be coupled to a patient for generating individual ECG data voltage signals. A switching matrix couples the leads to a plurality of differential circuits for coupling selected pairs of the ECG voltage signals to each of the differential circuits for generating differential ECG vector signals functionally related to the difference between selected pairs of the ECG voltage signals. A microprocessor is coupled to the leads and to the switching matrix and is operative to reset the switching matrix to uncouple one or more first leads from the differential circuits and for coupling one or more different ones of the ECG voltage signals to differential circuit formerly coupled to receive the voltage signal from the one or more first leads. An analog to digital converter is connected to the differential means for digitizing the ECG differential signals which are stored in the microprocessor and serially supplied to a modulator for phase modulating a carrier signal to be broadcast to a receiving and displaying unit. An LCD display indicates lead failure and a low battery condition.