This circuit with a bargraph scale was found in a 90s Popular Electronics. The circuit measures the intensity of a sound in three scales. R14 works as a sensitivity adjustment.
Recommended for automotive use, this circuit is used to indicate the activation of functions. The...
This 1969 Popular Electronics circuit was based on the then recently released BC109, today with...
This circuit provides an extremely stable, temperature-compensated reference current. The circuit is...