This circuit mimics the heartbeat with the softest sound played through a small speaker. The circuit is from an Electronics Now issue of January 1997.
This circuit was obtained from a Hands On-Electronics, an American magazine from January 1987. This...
Using the CA3140 in the figure we have a comparator that goes low in the window voltage space. The...
This circuit is from a Popular Electronics from the 90's. The circuit activates a buzzer with...