themotorman:
THey are as you described external and I don't have any way to connect to the Arduino except as a serial line. I am hoping someone will have some idea of what CMOS logic chips might do the job. I realize that this is not a simple problem but I am willing to build the PCB to put the chips on it. Just haven't worked with CMOS for some time and need some help with the CMOS family, decoders, etc... also need to take the logic output and have a way to read the data. I did think that a way would be to use 2 MEGAs, since that would give me enough inpins and then send the data from these to the remote ARduino via the serial line. Although not cheap it it seems that it might be the simplest... Opins?
Well before you start designing something one really needs to understand the circuitry the existing switching is wired in. There are questions like is there a common ground used in the existing wiring and connection available for any new logic or arduino additions. Are the voltage states always defined electrically, or is there a 'floating input pin' possible problem to be aware of? I would not start the effort or expense of such a project without a compete electrical schematic of what you are working with. At least that is my advice.
Lefty