This simple radio was found in a Popular Electronics from the 90s. L1 and L2 have 100 turns on a toroidal core and L1 have a socket on the thirtieth turn.
A circuit for controlling the temperature of a heating element was found in a Mullard transistor manual...
We found this circuit in a 1992 Popular Electronics. The circuit has an optical sensor with LED...
I found this circuit in an old English magazine from 1979, but it can be easily assembled with...