This circuit was found in an American 1980s documentation. It analyzes the exhaust gas of a vehicle using a special sensor. The indicator is a milliamperimeter.
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 =...