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 can be found in other projects in this site. When S1 is open the circuit produces...
This amplifier was found in an Electronics Now from the 90s. The FETs are part of a CD4007CB. |...
Found in a 90s Radio Electronics, this circuit is intended to trigger a relay when the current in...