digiboard (or digicard)
Digiboard or digicard is a generic name for a serial port card made by Digi International. While the typical PC comes with two serial ports, a compatible digiboard has the capability to add an additional four, eight, or 16 additional serial ports to a system.
A common use of a digiboard is to expand the services of a remote access server such as Microsoft RAS (Remote Access Server) for NT. It can also be used to expand a terminal server that accepts serial connections. Digiboards work with Windows, NetWare and most UNIX operating systems.