PCMCIA networking cards allow a host computer to connect to a network for data transmission and communication. They take their name from the Personal Computer Memory Card Association (PCMCIA), the organization which develops and maintains standards for PCMCIA cards. PCMCIA networking adapters include the following card types: modem cards, fax cards, local area network (LAN) cards, and wireless LAN cards. For each card type, product specifications include network protocol, card features, and power requirements. Typically, PCMCIA networking cards operate with 3.3-V and/or 5.5-V power. Memory buffer and data transfer rate are additional performance specifications to consider.
Network protocol is the most important specification to consider when selecting PCMCIA networking cards. Choices include 10Base-T, 10Base-2, and Fast Ethernet; token ring; and integrated services digital network (ISDN). For ISDN cards, there are two interface types: S/T and U. On an ISDN modem, the S/T interface is where other ISDN devices connect. ISDN devices also need an NT1 terminator between the ISDN device and the wall jack. The U-interface connects NT1-terminated ISDN devices to the telephone company's ISDN wall jack. Often, ISDN devices are equipped with this U-interface for a direct connection. Additional network specifications for PCMCIA networking cards include connector type (RJ-45 or BNC) and whether the card is tethered or wireless. Tethered network cards (non-wireless) are physically connected to the telephone lines.
Card features for PCMCIA networking cards include card form factor and data bus width (8, 16, or 32 bits). There are several choices for form factor. Type I cards are 54 mm x 85.4 mm, and can be up to 3.3 mm thick. Type II cards are 54 mm x 85.4 mm, and can be up to 5.5 mm thick. Type III cards are 54 mm x 85.4 mm, and can be up to 10.5 mm thick. Type IV cards have not yet been ratified by the PCMCIA consortium; however, their size is expected to be 54 mm x 85.4 mm with a thickness of 18 mm. Additional form factors for PCMCIA networking cards include SmartMedia Card, CompactFlash, Miniature Card, Solid State Floppy Disk (SSFDC), and MultiMediaCard (MMC).