This circuit was found in an old documentation, being able to generate signals of frequencies in the range of 50 to 100 MHz. The components are of the time.
This filter for the 300 Hz to 3 kHz range was found in an American documentation from the 90's....
The battery is charged by the photocell that keeps the low consumption beacon in the dark. The...
This is the typical circuit of an FET amplifier stage in the common source configuration. The circuit is...