It is incredible what some used to do, I once used a day or two trying to document an old logical system that was using 20-30 relays and contactors by tracing t

It is incredible what some used to do, I once used a day or two trying to document an old logical system that was using 20-30 relays and contactors by tracing the wires. Did end with giving up and had it rewritten in PLS-code. The old system was created a long time before I started working there by someone who where good at that kind of work and never learned to code in PLS. I don't know how it is done now, but at least 20 years ago more advanced systems where expensive and creating something using logical gates was what we where used to, so used that for simple systems. In some ways creating something using logical gates and get it to work is like doing something simple with command line tools instead of writing lots of code to do it