When the voltage in the circuit exceeds the value set in the trimpot, the LED goes off and, if a low current buzzer is used, it rings. The circuit is from American documentation from 1999.
This circuit was found in an old American publication. It makes use of an integrated circuit...
This circuit was found in an Electronics Now from the 90's. The integrated regulator circuit and...
This circuit was obtained in a publication from the 1980s. The coil can be the secondary winding of a...