Two 555s and a quad NAND-gate IC can simulate an electrocardiograph signal and a -y-wave radioisotope signal for applications in nuclear medicine. This circuit synchronizes the radioisotope signal to the EKG signal. You can use the circuit`s outputs to test, for example, microprocessor-based software that calculates the left ventricular ejection fraction before you use the software in clinical applications. IC1. a 555 timer, provides a positive-going pulse train that simulates an EKG signal.
A 10-KO potentiometer provides frequency adjustment. The other 555 timer, configured as a pulse-position modulator, provides the simulated -y-wave activity.