We find this encoding circuit in an American 1980s amateur radio documentation. The circuit can be implemented with equivalent modern components.
This circuit is from the 1990 Motorola Linear Databook. The circuit can be applied to other...
Found in a 90's EDN this circuit can be used as a shield. The transistor is a general-purpose type and the...
Suggested by Harris in documentation from the 80s, this circuit uses components from that time. It...