This circuit was found in 80's Popular Electronics. The components used are common and the number of indication channels (LEDs) can be changed.
This circuit is suggested by the National Semiconductor Linar Applications Handbook, controlling a DC motor...
This balance control for the channels of a stereo system was found in a 1969 Mullard...
This circuit produces the ticking of a clock on a common piezoelectric transducer. The circuit has an...