An ECG monitoring device with the use of audiofrequency modulation is proposed. In this device, ECG wave form is modulated in pulse frequency and converted into symmetric square wave through flip-flop circuit. The frequency corresponding to the base line of ECG is chosen between 400 to 800 Hz and maximum sensitivity is about 300 Hz/mV. Experimental results indicate that several features of ECG wave form such as arrhythmias, P or T wave inversion, S-T segment depression and extrasystoles can easily be differentiated.
This method is advantageously applicable not only to a long-term ECG monitoring but to portable ECG device or to ECG transmission through conventional telephone lines.