This circuit was obtained from an Electronics Now from the 90's. It generates the dial signal and the ring tone, serving for testing as well as for demonstrations.
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...