Found in a 90s EDN, this circuit is indicated for power control through a 4-20 mA line. The circuit makes use of optical couplers of the time.
This power supply is protected from shorts in the load. The BD135 must be mounted on a heatsink...
This circuit appears in various parts of this site and this section, with diverse origins. This is from...
This powerful amplifier with output in complementary symmetry is from an old documentation....