This circuit for very long-time intervals was found in the March 1993 Radio Electronics magazine. Times of several days or even weeks can be achieved depending on the value of C1.
This tuned circuit was found in a 1966 Electronic Circuit Handbook. The transistor can be any...
This circuit was published in an English magazine from 1980. The magazine no longer exists, but...
Found in American documentation, this circuit uses an automotive ignition coil to generate 20 kV. The...