Many types of external computer equipment have a serial ports to communicate with host PCs. ACCES I/O has Communication Cards for all of the popular protocols you may find on this type of equipment (RS-232, RS-422 and RS-485), ranging from a single port to eight ports on a single card. There are also optically isolated versions of some of these cards to ensure effective data transmission on long communication lines, even in electrically noisy environments. Having optical isolation is like having data insurance.
RS-485 and RS-422 have significant advantages over RS-232 as they use differential drivers instead of driving just one wire. This allows the cables in RS-485 and RS-422 applications to be up to 4000 feet, where RS-232 has a limit of 50 feet. See the table below for a comparison of cable length vs. baud rates.