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 the July 1994 issue of Electronics Now magazine. The circuit can use...
The transistors in this 80's documentation project may be BC548, the most modern equivalents of...
This circuit was found in an Electronic World of 1968. The circuit uses power transistors of the...