Optical potentiometer (CB22159E)

This voltage-controlled potentiometer using an LDR was found in an English documentation. LDR is common and LED of any type.

Neon Power Monitor (CB24103E)
This simple neon lamp power indicator circuit was found in the January 1971 Radio Electronics...
1-Transistor AM Radio (CB18380E)
This elementary receiver with only one germanium transistor was found in a Japanese publication from the...
Regenerative receiver (CB22273E)
This simple 1 transistor circuit was found in an American documentation from the 60's. The...