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.
In this phase shift circuit, the transistor can be any general-purpose transistor. The circuit is from...
This simple circuit was obtained from Popular Electronics in December 1990. The magazine no longer...
This circuit was found in an old American documentation. Its purpose is a proportional scanning signal...