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.
We found this circuit in a 1970 publication by General Electric. The components can be changed...
This source is used to supply circuits with operational amplifiers, being originally created for...
Suggested by American documentation from 1968, this circuit divides the frequency of synchronized...