This circuit with the ULN3784B appeared in the October 1984 issue of Radio Electronics magazine. It can typically be powered from 9 to 24 V.
We found this junction tester circuit in an old English documentation. The circuit serves to check...
This circuit can generate signals up to 100 kHz. Found in documentation from the 1980s, it makes...
Found in American documentation from the 70s, this circuit uses components of the time, uncommon...