This circuit was obtained from Radio Electronics magazine, October 1987. The circuit uses a triac to control the heating element current. The transistors are general purpose.
This conventional series reducer circuit reduces the voltage of a 12 V battery to the selected value...
In the figure we have a converter that generates a negative voltage from a positive voltage...
This circuit covers the bands from 1.8 to 150 MHz, with plug-in coils whose characteristics are...