Symmetrical power supply (CB21691E)

In the figure we have a symmetrical power supply stabilized by a zener diode. Transformer and zener diodes can be swapped to obtain other voltages.

MAX77874 Quad Phase Buck Controller - Maxim
High performance 16 A Buck regulators capable of operating at 2.7 to 4.8 V voltages and 0.25 to...
10 meters band receiver (CB23590E)
This circuit is from a Radio Electronics from February 1959. The circuit has a speaker output and...
Transistor Hartley Oscillator (CB4576E)
This circuit consists of a single Hartley oscillator using a bipolar transistor that can generate...