We found this circuit for musical instruments in the March 1992 Radio Electronics magazine. The circuit has outputs according to the desired scale from a crystal oscillator at the indicated frequency.
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...