Check out Umair’s Digital oscilloscope, it was intended as an entry for the open 7400 Logic Competition. Unfortunately, it was entered late, and won’t be competing in the competition. We’re sorry for them, as this seems like an awesome effort.
The oscilloscope has a bandwidth of 1KiloHertz. Yet it can just show the signal applied at its terminals, it does not have a facility to measure the voltage level. The voltage can be measured using some other sort of technique.
Via the contact form.