This circuit was obtained from an American 80's documentation. The balanced mixer can be shown in CB4234. The circuit is for controlling RF signals in a modulation system.
The component used in this regulator is not common today. The switching circuit is from an 80's...
This excellent amplifier with complementary symmetry output stage was taken from one of my audio...
This circuit is recommended by Texas Instruments in the datasheet of the TL317, equivalent to...