Cardial conitor apparatus

Claim 1

IN A CARDIAC MONITOR, THE COMBINATION COMPRISING: A PAIR OF TERMINALS ADAPTED FOR CONNECTION TO SPACED PORTIONS OF THE BODY OF A PATIENT, A CASE ADAPTED FOR ATTACHMENT TO THE FOREARM OF A HUMAN PATIENT CONNECTED TO ONE OF SAID TERMINALS, A CIRCUIT IN SAID CASE CONNECTED TO SAID TERMINALS COMPRISING AN AMPLIFIER FOR AMPLIFYING ELECTRICAL POTENTIALS ASSOCIATED WITH CARDIAC ACTION BETWEEN SAID TERMINALS, SAID AMPLIFIER INCLUDING FIRST, SECOND, AND THIRD AMPLIFIER STAGES, SAID FIRST AND SAID SECOND STAGES BEING RELATIVELY HIGH GAIN STAGES, A POWER SUPPLY CONNECTED IN SAID CIRCUIT TO PROVIDE OPERATING VOLTAGE FOR SAID AMPLIFIER, MEANS IN SAID CIRCUIT FOR PRODUCING SIGNALS INCLUDING AUDIBLE SIGNALS REPRESENTATIVE OF CARDIAC ACTION BETWEEN SAID TERMINALS IN RESPONSE TO THE OUTPUT OF SAID AMPLIFIER, DE-COUPLING MEANS FOR SUBSTANTIALLY PREVENTING VOLTAGE LOAD SURGES FROM REACHING SAID POWER SUPPLY, AND MEANS INCLUDING A RESISTOR-CAPACITOR NETWORK CONNECTED TO SAID SECOND STAGE FOR PREVENTING POWER SUPPLY VOLTAGE SURGES UNDER AUDIO LOAD FROM BEING REFLECTED INTO SAID FIRST AND SAID SECOND STAGES.