In the figure we have the configuration of series regulator protector suggested by Motorola in 1968 documentation. The transistors are of the time, being able to be used modern equivalents.
This circuit using components that are still common in our market was found in a 1987...
The varactor or varicap diode tunes the signal for listening to SSB signals on a common receiver. The...
This circuit that also serves to control LEDs and other loads is from a 1960 publication. The...