The figure shows a typical circuit of a variac with a special transformer with sliding adjustment of the winding turns. The circuit is from an Electronics Now magazine from December 1997.
This stable 20 MHz oscillator was suggested by the National Semiconductor's Linear Applications Handbook...
This buffer and driver is from the integrated circuit manual itself, the Linear Technology LT1206. The...
The transistors in this 1978 circuit can be BC548 and 1N4148 diodes. The electrolytic capacitors can be...