This simple audio signal tracer or follower can be made with a BC548 instead of the original transistor. The output is made in a small crystal phone. The power can be from 5 to 9V.
This small converter using Only one transistor was published in the Radio Electronics magazine from...
This circuit was found in a Popular Electronics of the 1990s. Its purpose is to expand the scale of...
This receiver was found in old English documentation and any general purpose NPN transistor can be...