A multiport serial card is installed in on the ISA or PCI bus of a PC. The card is helpful to the user because it provides many serial ports in the place of one, and so many computer users now use numerous external devices, such as video cameras, digital cameras, and scanners. Additionally, others use work-related equipment such as video-editing applications, faxes, or special printers for desktop publishing. At one time, serial cards were mainly used for connecting up many modems to serial ports. Today, several modems can now be built into an internal card. For this reason, multiport serial cards are not used as commonly as they were before.

Each multiport card has a number of external connecters (DB-25 or RJ45) so that one may connect up a number of devices (modems, terminals, etc.). Each such physical device would then be connected to its own serial port. It then requires a USB serial adapter.  There are dozens of different serial ports and adapters that can be used for various applications. For example, a video splitter requires one set, but a scanner or fax would require an entirely different set unique to those machines.

Finally, because there is limited space on the external-facing part of the card, sometimes there is not enough space to hold all the serial port connectors. In this case, the connectors may be on the ends of cables that extend from the card. Or, they can be on an external box that is connected by a cable to a multiport card.