Abstract: An ambulatory arrhythmia detection and ECG recorder senses both tachycardia and bradycardia conditions and activates a tape recorder to record the ECG for a period of 15 seconds after an arrhythmia is detected. Tachycardia and bradycardia conditions are sensed by converting the QRS component signals of the ECG into a pulse train which is a real time representation of the patient's actual heartbeat and then measuring the time between pulses utilizing two different oscillator controlled counter circuits. The first circuit indicates a tachycardia condition if the time between pulses is less than 500 milliseconds (120 beats per minute) or some other time preset by a doctor and the second circuit indicates a bradycardia condition if the time between pulses is greater than 1200 milliseconds (50 beats per minute) or some other time preset by a doctor.