This circuit was found in an Australian publication from 1991. It is a transmitter that transmits a signal when it detects moisture. The range is on the order of a few tens of meters.
This circuit was found in an American documentation from the 60's. The transistors are from the...
This oscillator is indicated for the adjustment of FI of FM radios, having its frequency...
This configuration triggers an external circuit or simply an LED for time given by R1 and C1 (T =...