This circuit for multiple sound inputs was found in a Radio Electronics from January 1992. It consists of a Bargraph connected to a multi-input mixer.
With the configuration shown in the figure, a single pulse for a counter can be obtained from a...
With calibrated RV1 it is possible to find a zener diode voltage. The integrated circuit is 0 741...
This circuit was found on an 80's Ham Radio. The transistor admits equivalent. The circuit can...