This power control from a 1968 Motorola manual shows how to use a contemporary diac as a zero-crossing detector. The SCR is of the type depending on the power of the load.
For experiments with ionization chambers and Geiger valves this circuit generates high voltage from...
This control allows to start or stop a motor up to 3 or 4 A with a low intensity signal. The...
The battery is charged by the photocell that keeps the low consumption beacon in the dark. The...