This converter was found in the June 1991 issue of Radio Electronics magazine. The circuit uses common circuits at the time and its operating range can be changed.
This circuit is from a 1974 publication, but it can still be easily assembled today with BC548...
Found on Popular Electronics in the 1980s, this circuit detects a change in air pressure using a...
This 3-transistor amplifier stage was found in documentation from 1963. The transistors are made...