This simple logic level tester was found in Radio Electronics from the 90s. The inverters are of the 4009 type and the power comes from the circuit being analyzed.
Found in American documentation from the 1970s, this circuit employs an integrated circuit from...
This circuit was obtained in the publication 101 Electronics Projects of 1979. The circuit can be...
This assembly circuit using a small motor as a generator was found in Radio Electroics magazine from...