Abstract: A circuit monitors electronic devices which require continuous clocking for non-destructive operation. The circuit samples a repetitive signal, such as a clock, from a device of interest (DOI). If, for whatever reason, the clock signal becomes absent, the circuit responds by deactivating the DOI. If the clock revives or becomes intermittent the circuit will not reactivate the DOI. The circuit will reactivate the DOI only upon application of an explicit reset signal. The circuit is all digital and therefore technology independent, and provides for precise control of the deactivation response time.