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 isolated shield is from an old documentation, making use of an operational one of the time. It...
This circuit can be used with receivers to attenuate signals that may cause interference. The...
In this circuit of an American documentation of the 90s, when the light is cut, we have the...