Found in American documentation from the 1990s, this circuit generates a whistling sound when applied to an amplifier. The power supply must be symmetrical.
P1 on this Radio Shack circuit is a 6 V lamp with current up to 500 mA depending on Q2. The...
This simple touch alarm, found in a 1995 documentation, uses common components and a triac to...
With the micro voltage regulator shown in the figure, we can design a power supply for small...