This circuit was found in an old American publication. The transformer is the type of output found in old transistor radios. The transducer is crystal headphone.
One of the problems with common 3-terminal regulators is that the internal reference, normally 1.25 V,...
This circuit found in French documentation, works with 15 V logic, but can be modified to TTL or 5...
We found this circuit in a 1972 documentation. The transistor, in fact, is a unijunction that can...