This circuit triggers an alarm in the event of a power failure. The circuit is from an 80's documentation, being powered by 9 V battery. The parts are common today.
This 1995 circuit uses an audio amplifier that is no longer common today. However, other...
The tone produced by this circuit attract fishes. The circuit is installed into a small can and...
This circuit is from Mullard 1969 documentation. The circuit operates at a relatively high supply...