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.
Found in September 1984 Radio Electronics issue this circuit has adjustable pulse width and...
This low power circuit for the FM band was found in a spy book from the 90s. The tunnel diode is...
This circuit was found in a 1987 edition of the United States' Hands On Electronics magazine. The...