The purpose of this circuit found in an old Elektor is to light a lower power lamp when the bigger one burns out. The loads depend on the triacs.
This simple 3-transistor circuit for short-range headphone listening was found in a Radio...
This circuit for the AM band with two transistors was found in the June 1960 Radio Electronics magazine....
We found this circuit in a 1978 publication. It can be implemented with modern transistors like...