This circuit can be used as an answering password system in a store, office, or other location. The circuit is from Intersil using components of the time. The circuit is from the 80's.
This circuit uses only passive components and must be tuned to the operating range. The circuit is...
This circuit is found in a 1975s documentation for radio amateurs. It was developed to recognize a...
This configuration triggers an external circuit or simply an LED for time given by R1 and C1 (T =...