Found in a Raytheon transistor manual from the 1950s, this circuit uses one of the first commercially available transistors, the CK722. The circuit is for using a small speaker as a microphone.
We found this circuit in an old oscilloscope publication. With it, it is possible to observe the B...
We found this circuit in an Electronic Engineering from the 90s. It applies to any logical family....
This circuit is from a documentation for 1976 radio amateurs. We can implement this circuit with...