I will only have one external 4-pin connector (or 3-pin if I can ignore one of the RS-485 lines--read on for explaination). That single connector will be fed by either a RS-232 signal or a RS-485 signal but not both at any given time.
If I have both types of receivers, I could OR them together, but I was not certain how it would work with one receiver always receiving slightly out-of-spec voltage levels.
Is there another method I can use using one receiver but will not be hurt by voltage levels from both types of transmissions? The distance is less than 100 feet and I can use 9600 BAUD so I think I can ignore one of the RS-485 lines if it would help.