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.
This nice analog indicator circuit was found in the January 1974 issue of Radio Electronics...
The purpose of this circuit is to increase the current of a MAX1735 regulator to obtain an output...
CMOS gates such as 4001 or 4011 can be configured as inverters and used in the circuit shown where...