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 power supply was originally designed to power our next circuit (CB18672E) which consists of a...
This circuit allows the control of a low intensity audio signal from an external logic signal. The...
Found in a 1964 publication, this circuit makes use of transistors from the time. It operates on...