This low power circuit for the FM band was found in a spy book from the 90s. The tunnel diode is not an easy component to obtain and the power can be supplied with a single button cell.
This circuit allows you to read resistors up to 20 M ohms, converting it into voltage. The circuit is...
The circuit in the figure is a useful continuity test serving to check the condition of circuits and...
This circuit beeps when the sensor is triggered by the opening of the freezer door or other...