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 is used to obtain the synchronized activation of a mechanical battery clock. The...
ON Semiconductor Phototransistor Output Optocouplers Available from Mouser Electronics is the...
Found in an Electronic Design from the 80's, this circuit monitors a three-phase line, activating a...