The transistors of this circuit found in an English 1980s documentation may be the modern BC548 equivalents. The circuit is battery powered and the earphone must be crystal.
This circuit was found in a Japanese publication from 1971. The circuit uses components from the...
This circuit was obtained in an English publication of 1993. It is an amplifier for...
This is a commercial circuit for an AM radio with 4 transistors, published in a Japanese magazine in...