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.
I got this circuit from an English magazine from 1977. It can still be easily assembled, as the...
Found in documentation from the 1990s, this circuit supports equivalent transistors. The range is on...
We found this circuit in a 1972 RCA technical documentation. The comparator can be any type and C1...