This circuit was found in a 90s Popular Electronics. It produces a muted tone similar to that produced by a bell. The signal must be applied to an amplifier.
This circuit is from an old manual, but can be easily assembled as the integrated one is still...
The simple transistor test shown in the figure can be powered by a 9V battery. The test is for...
This regulator can use BD'136 as the main transistor and as a reference next to a BC548 zener. The...