Check out the two SERIO modules. Previously only available for our WinPLC product line, these serial port modules are a great addition to the Do-more PLC line-up, and allow connection of a wide range of serial devices, such as barcode scanners, scales, printers, modems, etc.
Both the H2-SERIO and the H2-SERIO-4 provide 3 additional ports and are a bargain at $185.00.
"Device abstraction" makes it easy to connect external devices - give then logical names and then refer to those names throughout your program code for ease and clarity.
...makes it possible to "talk" to almost any device by letting you define any non-standard data exchange (serial or Ethernet)!