This circuit was found in a 1945 publication. The circuit was stated to be part of a walk talkie. Note that, as it is a portable assembly, it was powered by batteries. The jack was for microphone insertion.
This circuit was obtained in the 1990 Motorola Linear Databook. The circuit uses a 139 series...
September 2017 - Intersil's ISL850x Synchronized Buck Regulators can be ordered from Mouser...
Suggested by Texas Instruments in 1980s documentation, this circuit uses a component of the era....