Found in a PE Hobbyst Handbook of 1991, this circuit was originally proposed to time photographic baths in developing rooms but can be used for other purposes. The circuit beeps at 30-second intervals.
In a voltage follower the gain is unitary. Input impedance is too high and output impedance too low....
This simple sensitive circuit was suggested in a July 1992 Radio Electronics issue. The relay is a...
This circuit generates sine low-frequency signals. The frequency depends on the twin-T network....