Optical potentiometer (CB22159E)

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

Field strength meter (CB7358E)
This tuned circuit was found in a 1966 Electronic Circuit Handbook. The transistor can be any...
Analog to Digital Converter (CB21841E)
This circuit was found in Ferranti's 1974 transistor manual. Transistors are general purpose types...
Bargraph Humidity Indicator (CB11519E)
This circuit was found in a Popular Electronics from 1991. The transistor could be the BC548. The...