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.
This circuit is from old documentation, but can be adapted to use modern components. Power...
This circuit makes use of older operational amplifiers, but can be designed on the basis of modern...
This circuit can be used in 0,5 to 37 V Power supplies and output currents up to 3 A. The...