This circuit was found in the March 1997 Electronics Now magazine. It uses a common analog indicator and the transistor is a general purpose one.
8E) This siren was found in a 1989 documentation. It uses only transistors and includes two power...
We found this circuit, which appears with variations on this site, in a European documentation from the...
The operational amplifier used in this configuration is of an uncommon type today. The circuit can be...