This circuit was found in an Electronic Design from 1964. The components are from that time and can be replaced by equivalents. The modulation ranges from 0.25 to 0.75 of the 20 kHz pulses.
Suggested by Sprague in the 1980s documentation, this circuit can control three-phase AC motors....
This switched filter was found in the 1969 documentation. The FET should be current-matched and eventually...
The frequency of the blinking of this circuit is given by the capacitor that can have its value...