I have a circuit board on a 70's pinball machine. Its the logic for scoring from the playfield, among other things. I took a college course 15 years ago and digital was one of the items covered. I remember most of the material, but I was always confused (and still am) about combining several ics to make circuits work, concerning highs and lows. is there anyone here who can give a hand with this? the circuits are fairly simple, 2 ics.