This circuit is from the 80's documentation. The integrated circuit is from the time but can be implemented with modern equivalents. The power supply must be symmetrical.
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 =...