When the voltage supplying the circuit falls below the zener value, the LED lights up, and if a low current buzzer is used, it is activated. The circuit is from a 1999 American publication.
This two-port monostable of the 4001 was suggested by an article in the April 1988 Radio...
We found this circuit in a documentation from the 70s. Semiconductors are from the era and can be...
This circuit is from 1992 documentation. The transistor can be a TIP42 with a good heat sink for...