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.
This circuit is from a 1976 technical documentation, and there may be difficulties in obtaining the...
This circuit consists of an electret microphone amplifier powered by a 12 V voltage. A regulator is...
When the power is cut off, this circuit keeps the flashlight on for a while, allowing it to be...