Found in American documentation from 1968, this circuit has an acute cut-off of the frequency to which it is tuned and which depends on RC. Transistors may be modern equivalents of general use.
In the figure we have the way to implement a voltage doubler in a simple source. The component values...
This beacon causes an LED to flash with the mains voltage. The frequency depends on the capacitor. For...
This circuit was found in an American documentation two years 80. The MOSFET is of double port,...