This circuit was found I a 1965 Radio Schack documentation. The transistors are from that time, admitting equivalents. The transformer has 500 ohm primary and secondary depending on the speaker.
This circuit was found in a 1970 IEEE publication. The circuit functions as a voltage controlled...
Found in a documentation from the 90s, this circuit limits and amplifies a voice signal in the 800...
This gas sensor circuit was found in July 1976 Radio Electronics magazine. The TGS sensor was a...