This dual balanced modulator configuration was obtained in a 1980s telecommunications documentation. The circuit makes use of transformers and the diodes are commonly used.
This 13.8 V transistorized power supply with a current capacity of 20 A has a protection system...
This circuit that can only be used with simple resistive and inductive loads (never electronic) was...
This circuit is from an 80's publication. It makes use of small 6 V x 50 mA incandescent lamps....