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.
In the figure we have the basic way of using the 3-and-a-half-digit counter 7107. The circuit is...
We found this simple outlet tester using neon lamps in a Radio Electronics magazine from August...
The figure shows a simple way to obtain a negative voltage from a common source configuration. The circuit is...