The switches are for assigning specific addresses to each plug. For example, the first plug in the lineup would be assigned A1, the second A2 etc. The first two DIP switches assigns the letter for the addressing and the second two determine the numeric range, either 1-8 or 9-16. So for example, you could set it up to use the letter A and numbers 1-8. The plugs would be addressed A1 - A8. Your programming would reference these plug addresses and you would plug the correct device into the corresponding plug referenced in your programming.