This longwave signal booster circuit was found in the 1995 Encyclopedia of Electronic Circuits Volume 5. Note the dimensions of the board. The transistor is a general-purpose transistor.
Found in a 1990s American technical brochure, this circuit is intended for alarms that use as...
This control for bass, midrange, and treble was found in the March 1995 issue of Electronics Now...
Found in a 1965 General Electric documentation, this circuit is intended to control a 150 W lamp...