Please check carefully the supplier availability and longevity of the 26LS31 and 26LS32 chips before you commit them to new designs that will go into volume production. Some manufacturers that made these chips are out of production on them. I loved those chips for use on board designs for interfacing long distance device interfaces such as encoders, proximity detectors, and limit switches. The last time I designed them in I had to find alternate devices to use because of availability issues.

Michael Karas