If you have multiple printer chained off of one workstation, you will need to be sure each printer has a unique IDN number. All IDN printers should be set to COM4.
On the printer for IDN1, be sure switch 4 is the only switch on, for IDN 2 be sure switch 3 is the only switch on. If you were to use IDN 3 it would be switches 3 and 4 on.
-Tim