This simple audio and RF signal tracker was found in a Japanese publication in 1967. The transistors are made of germanium and the headphone is made of crystal.
This simple MW radio does not need an external antenna to pick up local stations. It was found in a...
This is a typical ohmmeter circuit with 50 uA analog instrument. The circuit was found in Radio...
This very simple circuit turns on an LED when an object interrupts the light that falls on the...