PCMCIA cards may be used for various purposes such as to establish a communications link between portable computer users and corporate networks, the Internet and other on-line services from a wide variety of locations; to supplement the semiconductor memory of a personal or notebook computer; to store information or data for use by the host system; or to reconfigure the host system in response to information stored in the card. Personal computers are fitted with I/O slots for exchanging electrical signals indicative of information according to standard transmission protocols, and particularly laptop or notebook computers, are provided with input slots that accept memory cards for exchanging data in accordance with the PCMCIA standard interface arrangement. PCMCIA cards are inserted in external slots of a laptop or handheld computer without the inconvenience of opening the computer. Their small size and portability allow easy interchange of applications by merely plugging and unplugging different peripheral cards into the external slots of the computer or other electronic device. Common applications available in PCMCIA format include modems, wireless communicators, and memory boards. The PCMCIA formats have proven to be popular for wireless modems. Typically a radio converts an input radio frequency signal to an analog baseband signal which is sent to a processor. This analog baseband signal is converted to digital data in the processor. The digital data is then output across the PCMCIA connector to the host device. The PCMCIA interface is a full featured and versatile method of accessing a wide variety of peripheral devices. The interface provides for optional feature support by the peripheral devices (PC cards). PCMCIA interface is designed to interface to devices with great disparity in access speeds. When the CPU or host adapter initiates a transfer to or from the PCMCIA device, the PC card can extend the access cycle to meet the needs of any slow hardware in the card. This allows PC cards with different access times to all share the same bus interface. An advantage of the use of PC cards over other connectivity mechanisms is the ease with which PC cards may be inserted and removed, making it easy to change from one device to another. PC cards typically contain their own microprocessors and memory storage registers, they can perform most if not all of the required processing functions internally. Therefore, by using a PCMCIA card to add functionality to a host computer, the user does not need to load large amounts of programming into the host computer or use large amounts of data storage, saving host computer resources for other applications. The PCMCIA can also be transformed into the other interfaces, such as PCMCIA to SCSI or PCMCIA to IDE (Integrated Drive Electronics or Intelligent Device Electronics), so as to allow the portable computer to use various interfaces of personal computers.

PCMCIA cards typically include a substrate, usually rectangular and in the form of a printed circuit board (PCB) which contains electronic components including integrated circuit packages. All three card types measure the same length (85.6 mm) and the same width (54.0 mm), and differ only in overall thickness. The Type I card has a thickness of 3.3 mm; the Type II card, 5.0 mm; and the Type III card, 10.5 mm. The printed circuit board is attached along one of its edges to a multiple connector typically including a connector of molded plastic having multiple contacts for electrically connecting the card to the host system by way of a port or slot. Memory cards compatible with PCMCIA standard are used to install memory in a small form factor for digital computer systems. The memory cards contain a printed circuit board with a 68-pin interface at one end which is insertable through a slot into a PCMCIA compatible interface of a digital computer system. When inserted, memory on the circuit board, typically in the form of flash or SRAM memory components, is accessible to the digital computer system. At one end of a PCMCIA memory card is an interface section which provides a female portion of a connector that mates with a male end in a receiving device. A card ejection mechanism is mounted to a side arm of the connector for ejecting the card from a card-receiving slot thereof. The card ejection mechanism commonly comprises a movable plate for removing an inserted card from the connector, a push rod disposed in a guide, and a pivotable ejector arm coupling the movable plate and the push rod together. A PCMCIA card further includes a molded plastic, insulative frame and a sheet metal cover including upper and lower cover panels enclosing the PCB and having forward margins secured to upper and lower surfaces of the plastic connector. The metal cover not only protects the PCB, but also acts as a shield against electromagnetic interference. A PCMCIA card connector typically comprises a header adapted for accommodating a PCMCIA card with a plurality of passageways defined therein and arranged in rows for receiving a corresponding number of terminals. Each terminal comprises a contact portion for mating with a corresponding contact of an inserted card, and a tail portion downwardly extending from the header for connecting with a (PCB). Generally, a PCMCIA controller, which is provided as one of the PCI devices in a personal computer system, is configured to have an interrupt processing function in order to allow a known plug-and-play capability of a PC card.