This circuit was found in a Popular Electronics from the 90's. The output signal can be applied to a headphone or speaker. The microphone can be a piezoelectric tweeter capsule or other type.
This circuit is intended to limit the ringing time of a bell. Even if the button is kept pressed for...
We found this circuit in the November 1974 Radio Electronics magazine. The frequency depends on C1...
This conventional 12 V power supply stabilized with 2 A current was found in a 1995 documentation. Its...