Found in documentation from the 1980s, this circuit can have several adaptations to use modern transistors and LEDs instead of the lamp. The power supply voltage can also be changed.
This capacitive approach alarm circuit was found in a 2002 documentation. The wire to the sensor...
This circuit uses a common digital clock to activate a relay at a programmed time. The circuit takes...
The integrated audio amplifier used in this project is not very common today, but more modern...